diff --git a/Documentation/git-mktag.txt b/Documentation/git-mktag.txt
index fa6a756123..17a2603a60 100644
--- a/Documentation/git-mktag.txt
+++ b/Documentation/git-mktag.txt
@@ -3,7 +3,7 @@ git-mktag(1)
 
 NAME
 ----
-git-mktag - Creates a tag object
+git-mktag - Creates a tag object with extra validation
 
 
 SYNOPSIS
@@ -11,25 +11,52 @@ SYNOPSIS
 [verse]
 'git mktag'
 
+OPTIONS
+-------
+
+--strict::
+	By default mktag turns on the equivalent of
+	linkgit:git-fsck[1] `--strict` mode. Use `--no-strict` to
+	disable it.
+
 DESCRIPTION
 -----------
-Reads a tag contents on standard input and creates a tag object
-that can also be used to sign other objects.
 
-The output is the new tag's <object> identifier.
+Reads a tag contents on standard input and creates a tag object. The
+output is the new tag's <object> identifier.
+
+This command is mostly equivalent to linkgit:git-hash-object[1]
+invoked with `-t tag -w --stdin`. I.e. both of these will create and
+write a tag found in `my-tag`:
+
+    git mktag <my-tag
+    git hash-object -t tag -w --stdin <my-tag
+
+The difference is that mktag will die before writing the tag if the
+tag doesn't pass a linkgit:git-fsck[1] check.
+
+The "fsck" check done mktag is stricter than what linkgit:git-fsck[1]
+would run by default in that all `fsck.<msg-id>` messages are promoted
+from warnings to errors (so e.g. a missing "tagger" line is an error).
+
+Extra headers in the object are also an error under mktag, but ignored
+by linkgit:git-fsck[1]. This extra check can be turned off by setting
+the appropriate `fsck.<msg-id>` varible:
+
+    git -c fsck.extraHeaderEntry=ignore mktag <my-tag-with-headers
 
 Tag Format
 ----------
 A tag signature file, to be fed to this command's standard input,
 has a very simple fixed format: four lines of
 
-  object <sha1>
+  object <hash>
   type <typename>
   tag <tagname>
   tagger <tagger>
 
 followed by some 'optional' free-form message (some tags created
-by older Git may not have `tagger` line).  The message, when
+by older Git may not have `tagger` line).  The message, when it
 exists, is separated by a blank line from the header.  The
 message part may contain a signature that Git itself doesn't
 care about, but that can be verified with gpg.
diff --git a/builtin/fsck.c b/builtin/fsck.c
index fbf26cafcf..821e7798c7 100644
--- a/builtin/fsck.c
+++ b/builtin/fsck.c
@@ -73,25 +73,7 @@ static const char *printable_type(const struct object_id *oid,
 
 static int fsck_config(const char *var, const char *value, void *cb)
 {
-	if (strcmp(var, "fsck.skiplist") == 0) {
-		const char *path;
-		struct strbuf sb = STRBUF_INIT;
-
-		if (git_config_pathname(&path, var, value))
-			return 1;
-		strbuf_addf(&sb, "skiplist=%s", path);
-		free((char *)path);
-		fsck_set_msg_types(&fsck_obj_options, sb.buf);
-		strbuf_release(&sb);
-		return 0;
-	}
-
-	if (skip_prefix(var, "fsck.", &var)) {
-		fsck_set_msg_type(&fsck_obj_options, var, value);
-		return 0;
-	}
-
-	return git_default_config(var, value, cb);
+	return fsck_config_internal(var, value, cb, &fsck_obj_options);
 }
 
 static int objerror(struct object *obj, const char *err)
diff --git a/builtin/mktag.c b/builtin/mktag.c
index 4982d3a93e..41a399a69e 100644
--- a/builtin/mktag.c
+++ b/builtin/mktag.c
@@ -1,179 +1,110 @@
 #include "builtin.h"
+#include "parse-options.h"
 #include "tag.h"
 #include "replace-object.h"
 #include "object-store.h"
+#include "fsck.h"
+#include "config.h"
 
-/*
- * A signature file has a very simple fixed format: four lines
- * of "object <sha1>" + "type <typename>" + "tag <tagname>" +
- * "tagger <committer>", followed by a blank line, a free-form tag
- * message and a signature block that git itself doesn't care about,
- * but that can be verified with gpg or similar.
- *
- * The first four lines are guaranteed to be at least 83 bytes:
- * "object <sha1>\n" is 48 bytes, "type tag\n" at 9 bytes is the
- * shortest possible type-line, "tag .\n" at 6 bytes is the shortest
- * single-character-tag line, and "tagger . <> 0 +0000\n" at 20 bytes is
- * the shortest possible tagger-line.
- */
+static char const * const builtin_mktag_usage[] = {
+	N_("git mktag"),
+	NULL
+};
+static int option_strict = 1;
 
-/*
- * We refuse to tag something we can't verify. Just because.
- */
-static int verify_object(const struct object_id *oid, const char *expected_type)
+static struct fsck_options fsck_options = FSCK_OPTIONS_STRICT;
+
+static int mktag_config(const char *var, const char *value, void *cb)
 {
-	int ret = -1;
-	enum object_type type;
-	unsigned long size;
-	void *buffer = read_object_file(oid, &type, &size);
-	const struct object_id *repl = lookup_replace_object(the_repository, oid);
-
-	if (buffer) {
-		if (type == type_from_string(expected_type)) {
-			ret = check_object_signature(the_repository, repl,
-						     buffer, size,
-						     expected_type);
-		}
-		free(buffer);
-	}
-	return ret;
+	return fsck_config_internal(var, value, cb, &fsck_options);
 }
 
-static int verify_tag(char *buffer, unsigned long size)
+static int mktag_fsck_error_func(struct fsck_options *o,
+				 const struct object_id *oid,
+				 enum object_type object_type,
+				 int msg_type, const char *message)
 {
-	int typelen;
-	char type[20];
-	struct object_id oid;
-	const char *object, *type_line, *tag_line, *tagger_line, *lb, *rb, *p;
-	size_t len;
+	switch (msg_type) {
+	case FSCK_WARN:
+		if (!option_strict) {
+			fprintf_ln(stderr, _("warning: tag input does not pass fsck: %s"), message);
+			return 0;
 
-	if (size < 84)
-		return error("wanna fool me ? you obviously got the size wrong !");
-
-	buffer[size] = 0;
-
-	/* Verify object line */
-	object = buffer;
-	if (memcmp(object, "object ", 7))
-		return error("char%d: does not start with \"object \"", 0);
-
-	if (parse_oid_hex(object + 7, &oid, &p))
-		return error("char%d: could not get SHA1 hash", 7);
-
-	/* Verify type line */
-	type_line = p + 1;
-	if (memcmp(type_line - 1, "\ntype ", 6))
-		return error("char%d: could not find \"\\ntype \"", 47);
-
-	/* Verify tag-line */
-	tag_line = strchr(type_line, '\n');
-	if (!tag_line)
-		return error("char%"PRIuMAX": could not find next \"\\n\"",
-				(uintmax_t) (type_line - buffer));
-	tag_line++;
-	if (memcmp(tag_line, "tag ", 4) || tag_line[4] == '\n')
-		return error("char%"PRIuMAX": no \"tag \" found",
-				(uintmax_t) (tag_line - buffer));
-
-	/* Get the actual type */
-	typelen = tag_line - type_line - strlen("type \n");
-	if (typelen >= sizeof(type))
-		return error("char%"PRIuMAX": type too long",
-				(uintmax_t) (type_line+5 - buffer));
-
-	memcpy(type, type_line+5, typelen);
-	type[typelen] = 0;
-
-	/* Verify that the object matches */
-	if (verify_object(&oid, type))
-		return error("char%d: could not verify object %s", 7, oid_to_hex(&oid));
-
-	/* Verify the tag-name: we don't allow control characters or spaces in it */
-	tag_line += 4;
-	for (;;) {
-		unsigned char c = *tag_line++;
-		if (c == '\n')
-			break;
-		if (c > ' ')
-			continue;
-		return error("char%"PRIuMAX": could not verify tag name",
-				(uintmax_t) (tag_line - buffer));
+		}
+		/* fallthrough */
+	case FSCK_ERROR:
+		/*
+		 * We treat both warnings and errors as errors, things
+		 * like missing "tagger" lines are "only" warnings
+		 * under fsck, we've always considered them an error.
+		 */
+		fprintf_ln(stderr, _("error: tag input does not pass fsck: %s"), message);
+		return 1;
+	default:
+		BUG(_("%d (FSCK_IGNORE?) should never trigger this callback"),
+		    msg_type);
 	}
+}
 
-	/* Verify the tagger line */
-	tagger_line = tag_line;
+static int verify_object_in_tag(struct object_id *tagged_oid, int *tagged_type)
+{
+	int ret;
+	enum object_type type;
+	unsigned long size;
+	void *buffer;
+	const struct object_id *repl;
 
-	if (memcmp(tagger_line, "tagger ", 7))
-		return error("char%"PRIuMAX": could not find \"tagger \"",
-			(uintmax_t) (tagger_line - buffer));
+	buffer = read_object_file(tagged_oid, &type, &size);
+	if (!buffer)
+		die(_("could not read tagged object '%s'"),
+		    oid_to_hex(tagged_oid));
+	if (type != *tagged_type)
+		die(_("object '%s' tagged as '%s', but is a '%s' type"),
+		    oid_to_hex(tagged_oid),
+		    type_name(*tagged_type), type_name(type));
 
-	/*
-	 * Check for correct form for name and email
-	 * i.e. " <" followed by "> " on _this_ line
-	 * No angle brackets within the name or email address fields.
-	 * No spaces within the email address field.
-	 */
-	tagger_line += 7;
-	if (!(lb = strstr(tagger_line, " <")) || !(rb = strstr(lb+2, "> ")) ||
-		strpbrk(tagger_line, "<>\n") != lb+1 ||
-		strpbrk(lb+2, "><\n ") != rb)
-		return error("char%"PRIuMAX": malformed tagger field",
-			(uintmax_t) (tagger_line - buffer));
+	repl = lookup_replace_object(the_repository, tagged_oid);
+	ret = check_object_signature(the_repository, repl,
+				     buffer, size, type_name(*tagged_type));
+	free(buffer);
 
-	/* Check for author name, at least one character, space is acceptable */
-	if (lb == tagger_line)
-		return error("char%"PRIuMAX": missing tagger name",
-			(uintmax_t) (tagger_line - buffer));
-
-	/* timestamp, 1 or more digits followed by space */
-	tagger_line = rb + 2;
-	if (!(len = strspn(tagger_line, "0123456789")))
-		return error("char%"PRIuMAX": missing tag timestamp",
-			(uintmax_t) (tagger_line - buffer));
-	tagger_line += len;
-	if (*tagger_line != ' ')
-		return error("char%"PRIuMAX": malformed tag timestamp",
-			(uintmax_t) (tagger_line - buffer));
-	tagger_line++;
-
-	/* timezone, 5 digits [+-]hhmm, max. 1400 */
-	if (!((tagger_line[0] == '+' || tagger_line[0] == '-') &&
-	      strspn(tagger_line+1, "0123456789") == 4 &&
-	      tagger_line[5] == '\n' && atoi(tagger_line+1) <= 1400))
-		return error("char%"PRIuMAX": malformed tag timezone",
-			(uintmax_t) (tagger_line - buffer));
-	tagger_line += 6;
-
-	/* Verify the blank line separating the header from the body */
-	if (*tagger_line != '\n')
-		return error("char%"PRIuMAX": trailing garbage in tag header",
-			(uintmax_t) (tagger_line - buffer));
-
-	/* The actual stuff afterwards we don't care about.. */
-	return 0;
+	return ret;
 }
 
 int cmd_mktag(int argc, const char **argv, const char *prefix)
 {
+	static struct option builtin_mktag_options[] = {
+		OPT_BOOL(0, "strict", &option_strict,
+			 N_("enable more strict checking")),
+		OPT_END(),
+	};
 	struct strbuf buf = STRBUF_INIT;
+	struct object_id tagged_oid;
+	int tagged_type;
 	struct object_id result;
 
-	if (argc != 1)
-		usage("git mktag");
+	argc = parse_options(argc, argv, NULL,
+			     builtin_mktag_options,
+			     builtin_mktag_usage, 0);
 
-	if (strbuf_read(&buf, 0, 4096) < 0) {
-		die_errno("could not read from stdin");
-	}
+	if (strbuf_read(&buf, 0, 0) < 0)
+		die_errno(_("could not read from stdin"));
 
-	/* Verify it for some basic sanity: it needs to start with
-	   "object <sha1>\ntype\ntagger " */
-	if (verify_tag(buf.buf, buf.len) < 0)
-		die("invalid tag signature file");
+	fsck_options.error_func = mktag_fsck_error_func;
+	fsck_set_msg_type(&fsck_options, "extraheaderentry", "warn");
+	/* config might set fsck.extraHeaderEntry=* again */
+	git_config(mktag_config, NULL);
+	if (fsck_tag_standalone(NULL, buf.buf, buf.len, &fsck_options,
+				&tagged_oid, &tagged_type))
+		die(_("tag on stdin did not pass our strict fsck check"));
+
+	if (verify_object_in_tag(&tagged_oid, &tagged_type))
+		die(_("tag on stdin did not refer to a valid object"));
 
 	if (write_object_file(buf.buf, buf.len, tag_type, &result) < 0)
-		die("unable to write tag file");
+		die(_("unable to write tag file"));
 
 	strbuf_release(&buf);
-	printf("%s\n", oid_to_hex(&result));
+	puts(oid_to_hex(&result));
 	return 0;
 }
diff --git a/fsck.c b/fsck.c
index f82e2fe9e3..69d0049e4d 100644
--- a/fsck.c
+++ b/fsck.c
@@ -80,7 +80,9 @@ static struct oidset gitmodules_done = OIDSET_INIT;
 	/* infos (reported as warnings, but ignored by default) */ \
 	FUNC(GITMODULES_PARSE, INFO) \
 	FUNC(BAD_TAG_NAME, INFO) \
-	FUNC(MISSING_TAGGER_ENTRY, INFO)
+	FUNC(MISSING_TAGGER_ENTRY, INFO) \
+	/* ignored (elevated when requested) */ \
+	FUNC(EXTRA_HEADER_ENTRY, IGNORE)
 
 #define MSG_ID(id, msg_type) FSCK_MSG_##id,
 enum fsck_msg_id {
@@ -911,6 +913,16 @@ static int fsck_tag(const struct object_id *oid, const char *buffer,
 		    unsigned long size, struct fsck_options *options)
 {
 	struct object_id tagged_oid;
+	int tagged_type;
+	return fsck_tag_standalone(oid, buffer, size, options, &tagged_oid,
+				   &tagged_type);
+}
+
+int fsck_tag_standalone(const struct object_id *oid, const char *buffer,
+			unsigned long size, struct fsck_options *options,
+			struct object_id *tagged_oid,
+			int *tagged_type)
+{
 	int ret = 0;
 	char *eol;
 	struct strbuf sb = STRBUF_INIT;
@@ -924,7 +936,7 @@ static int fsck_tag(const struct object_id *oid, const char *buffer,
 		ret = report(options, oid, OBJ_TAG, FSCK_MSG_MISSING_OBJECT, "invalid format - expected 'object' line");
 		goto done;
 	}
-	if (parse_oid_hex(buffer, &tagged_oid, &p) || *p != '\n') {
+	if (parse_oid_hex(buffer, tagged_oid, &p) || *p != '\n') {
 		ret = report(options, oid, OBJ_TAG, FSCK_MSG_BAD_OBJECT_SHA1, "invalid 'object' line format - bad sha1");
 		if (ret)
 			goto done;
@@ -940,7 +952,8 @@ static int fsck_tag(const struct object_id *oid, const char *buffer,
 		ret = report(options, oid, OBJ_TAG, FSCK_MSG_MISSING_TYPE, "invalid format - unexpected end after 'type' line");
 		goto done;
 	}
-	if (type_from_string_gently(buffer, eol - buffer, 1) < 0)
+	*tagged_type = type_from_string_gently(buffer, eol - buffer, 1);
+	if (*tagged_type < 0)
 		ret = report(options, oid, OBJ_TAG, FSCK_MSG_BAD_TYPE, "invalid 'type' value");
 	if (ret)
 		goto done;
@@ -974,6 +987,21 @@ static int fsck_tag(const struct object_id *oid, const char *buffer,
 	}
 	else
 		ret = fsck_ident(&buffer, oid, OBJ_TAG, options);
+	if (!*buffer)
+		goto done;
+
+	if (!starts_with(buffer, "\n")) {
+		/*
+		 * The verify_headers() check will allow
+		 * e.g. "[...]tagger <tagger>\nsome
+		 * garbage\n\nmessage" to pass, thinking "some
+		 * garbage" could be a custom header. E.g. "mktag"
+		 * doesn't want any unknown headers.
+		 */
+		ret = report(options, oid, OBJ_TAG, FSCK_MSG_EXTRA_HEADER_ENTRY, "invalid format - extra header(s) after 'tagger'");
+		if (ret)
+			goto done;
+	}
 
 done:
 	strbuf_release(&sb);
@@ -1284,3 +1312,27 @@ int fsck_finish(struct fsck_options *options)
 	oidset_clear(&gitmodules_done);
 	return ret;
 }
+
+int fsck_config_internal(const char *var, const char *value, void *cb,
+			 struct fsck_options *options)
+{
+	if (strcmp(var, "fsck.skiplist") == 0) {
+		const char *path;
+		struct strbuf sb = STRBUF_INIT;
+
+		if (git_config_pathname(&path, var, value))
+			return 1;
+		strbuf_addf(&sb, "skiplist=%s", path);
+		free((char *)path);
+		fsck_set_msg_types(options, sb.buf);
+		strbuf_release(&sb);
+		return 0;
+	}
+
+	if (skip_prefix(var, "fsck.", &var)) {
+		fsck_set_msg_type(options, var, value);
+		return 0;
+	}
+
+	return git_default_config(var, value, cb);
+}
diff --git a/fsck.h b/fsck.h
index 69cf715e79..423c467feb 100644
--- a/fsck.h
+++ b/fsck.h
@@ -62,6 +62,15 @@ int fsck_walk(struct object *obj, void *data, struct fsck_options *options);
 int fsck_object(struct object *obj, void *data, unsigned long size,
 	struct fsck_options *options);
 
+/*
+ * fsck a tag, and pass info about it back to the caller. This is
+ * exposed fsck_object() internals for git-mktag(1).
+ */
+int fsck_tag_standalone(const struct object_id *oid, const char *buffer,
+			unsigned long size, struct fsck_options *options,
+			struct object_id *tagged_oid,
+			int *tag_type);
+
 /*
  * Some fsck checks are context-dependent, and may end up queued; run this
  * after completing all fsck_object() calls in order to resolve any remaining
@@ -94,4 +103,11 @@ void fsck_put_object_name(struct fsck_options *options,
 const char *fsck_describe_object(struct fsck_options *options,
 				 const struct object_id *oid);
 
+/*
+ * git_config() callback for use by fsck-y tools that want to support
+ * fsck.<msg> fsck.skipList etc.
+ */
+int fsck_config_internal(const char *var, const char *value, void *cb,
+			 struct fsck_options *options);
+
 #endif
diff --git a/t/t1006-cat-file.sh b/t/t1006-cat-file.sh
index 2f501d2dc9..5d2dc99b74 100755
--- a/t/t1006-cat-file.sh
+++ b/t/t1006-cat-file.sh
@@ -166,7 +166,7 @@ tag_content="$tag_header_without_timestamp 0000000000 +0000
 
 $tag_description"
 
-tag_sha1=$(echo_without_newline "$tag_content" | git mktag)
+tag_sha1=$(echo_without_newline "$tag_content" | git hash-object -t tag --stdin -w)
 tag_size=$(strlen "$tag_content")
 
 run_tests 'tag' $tag_sha1 $tag_size "$tag_content" "$tag_content" 1
diff --git a/t/t3800-mktag.sh b/t/t3800-mktag.sh
index d696aa4e52..86bfeb271e 100755
--- a/t/t3800-mktag.sh
+++ b/t/t3800-mktag.sh
@@ -12,10 +12,29 @@ test_description='git mktag: tag object verify test'
 # given in the expect.pat file.
 
 check_verify_failure () {
-	expect="$2"
+	test_expect_success "$1" "
+		test_must_fail env GIT_TEST_GETTEXT_POISON=false \
+			git mktag <tag.sig 2>message &&
+		grep '$2' message &&
+		if test '$3' != '--no-strict'
+		then
+			test_must_fail env GIT_TEST_GETTEXT_POISON=false \
+				git mktag --no-strict <tag.sig 2>message.no-strict &&
+			grep '$2' message.no-strict
+		fi
+	"
+}
+
+test_expect_mktag_success() {
 	test_expect_success "$1" '
-		( test_must_fail git mktag <tag.sig 2>message ) &&
-		grep "$expect" message
+		git hash-object -t tag -w --stdin <tag.sig >expected &&
+		git fsck --strict &&
+
+		git mktag <tag.sig >hash &&
+		test_cmp expected hash &&
+		test_when_finished "git update-ref -d refs/tags/mytag $(cat hash)" &&
+		git update-ref refs/tags/mytag $(cat hash) $(test_oid zero) &&
+		git fsck --strict
 	'
 }
 
@@ -23,10 +42,24 @@ check_verify_failure () {
 # first create a commit, so we have a valid object/type
 # for the tag.
 test_expect_success 'setup' '
-	echo Hello >A &&
-	git update-index --add A &&
-	git commit -m "Initial commit" &&
-	head=$(git rev-parse --verify HEAD)
+	test_commit A &&
+	test_commit B &&
+	head=$(git rev-parse --verify HEAD) &&
+	head_parent=$(git rev-parse --verify HEAD~) &&
+	tree=$(git rev-parse HEAD^{tree}) &&
+	blob=$(git rev-parse --verify HEAD:B.t)
+'
+
+test_expect_success 'basic usage' '
+	cat >tag.sig <<-EOF &&
+	object $head
+	type commit
+	tag mytag
+	tagger T A Gger <tagger@example.com> 1206478233 -0500
+	EOF
+	git mktag <tag.sig &&
+	git mktag --end-of-options <tag.sig &&
+	test_expect_code 129 git mktag --unknown-option
 '
 
 ############################################################
@@ -37,33 +70,33 @@ too short for a tag
 EOF
 
 check_verify_failure 'Tag object length check' \
-	'^error: .*size wrong.*$'
+	'^error:.* missingObject:' 'strict'
 
 ############################################################
 #  2. object line label check
 
 cat >tag.sig <<EOF
-xxxxxx 139e9b33986b1c2670fff52c5067603117b3e895
+xxxxxx $head
 type tag
 tag mytag
 tagger . <> 0 +0000
 
 EOF
 
-check_verify_failure '"object" line label check' '^error: char0: .*"object "$'
+check_verify_failure '"object" line label check' '^error:.* missingObject:'
 
 ############################################################
-#  3. object line SHA1 check
+#  3. object line hash check
 
 cat >tag.sig <<EOF
-object zz9e9b33986b1c2670fff52c5067603117b3e895
+object $(echo $head | tr 0-9a-f z)
 type tag
 tag mytag
 tagger . <> 0 +0000
 
 EOF
 
-check_verify_failure '"object" line SHA1 check' '^error: char7: .*SHA1 hash$'
+check_verify_failure '"object" line check' '^error:.* badObjectSha1:'
 
 ############################################################
 #  4. type line label check
@@ -76,7 +109,7 @@ tagger . <> 0 +0000
 
 EOF
 
-check_verify_failure '"type" line label check' '^error: char.*: .*"\\ntype "$'
+check_verify_failure '"type" line label check' '^error:.* missingTypeEntry:'
 
 ############################################################
 #  5. type line eol check
@@ -84,7 +117,7 @@ check_verify_failure '"type" line label check' '^error: char.*: .*"\\ntype "$'
 echo "object $head" >tag.sig
 printf "type tagsssssssssssssssssssssssssssssss" >>tag.sig
 
-check_verify_failure '"type" line eol check' '^error: char.*: .*"\\n"$'
+check_verify_failure '"type" line eol check' '^error:.* unterminatedHeader:'
 
 ############################################################
 #  6. tag line label check #1
@@ -98,7 +131,7 @@ tagger . <> 0 +0000
 EOF
 
 check_verify_failure '"tag" line label check #1' \
-	'^error: char.*: no "tag " found$'
+	'^error:.* missingTagEntry:'
 
 ############################################################
 #  7. tag line label check #2
@@ -110,7 +143,7 @@ tag
 EOF
 
 check_verify_failure '"tag" line label check #2' \
-	'^error: char.*: no "tag " found$'
+	'^error:.* badType:'
 
 ############################################################
 #  8. type line type-name length check
@@ -122,10 +155,32 @@ tag mytag
 EOF
 
 check_verify_failure '"type" line type-name length check' \
-	'^error: char.*: type too long$'
+	'^error:.* badType:'
 
 ############################################################
-#  9. verify object (SHA1/type) check
+#  9. verify object (hash/type) check
+
+cat >tag.sig <<EOF
+object $(test_oid deadbeef)
+type tag
+tag mytag
+tagger . <> 0 +0000
+
+EOF
+
+check_verify_failure 'verify object (hash/type) check -- correct type, nonexisting object' \
+	'^fatal: could not read tagged object'
+
+cat >tag.sig <<EOF
+object $head
+type tagggg
+tag mytag
+tagger . <> 0 +0000
+
+EOF
+
+check_verify_failure 'verify object (hash/type) check -- made-up type, valid object' \
+	'^error:.* badType:'
 
 cat >tag.sig <<EOF
 object $(test_oid deadbeef)
@@ -135,8 +190,48 @@ tagger . <> 0 +0000
 
 EOF
 
-check_verify_failure 'verify object (SHA1/type) check' \
-	'^error: char7: could not verify object.*$'
+check_verify_failure 'verify object (hash/type) check -- made-up type, nonexisting object' \
+	'^error:.* badType:'
+
+cat >tag.sig <<EOF
+object $head
+type tree
+tag mytag
+tagger . <> 0 +0000
+
+EOF
+
+check_verify_failure 'verify object (hash/type) check -- mismatched type, valid object' \
+	'^fatal: object.*tagged as.*tree.*but is.*commit'
+
+############################################################
+#  9.5. verify object (hash/type) check -- replacement
+
+test_expect_success 'setup replacement of commit -> commit and tree -> blob' '
+	git replace $head_parent $head &&
+	git replace -f $tree $blob
+'
+
+cat >tag.sig <<EOF
+object $head_parent
+type commit
+tag mytag
+tagger . <> 0 +0000
+
+EOF
+
+test_expect_mktag_success 'tag to a commit replaced by another commit'
+
+cat >tag.sig <<EOF
+object $tree
+type tree
+tag mytag
+tagger . <> 0 +0000
+
+EOF
+
+check_verify_failure 'verify object (hash/type) check -- mismatched type, valid object' \
+	'^fatal: object.*tagged as.*tree.*but is.*blob'
 
 ############################################################
 # 10. verify tag-name check
@@ -150,7 +245,7 @@ tagger . <> 0 +0000
 EOF
 
 check_verify_failure 'verify tag-name check' \
-	'^error: char.*: could not verify tag name$'
+	'^error:.* badTagName:' '--no-strict'
 
 ############################################################
 # 11. tagger line label check #1
@@ -164,7 +259,7 @@ This is filler
 EOF
 
 check_verify_failure '"tagger" line label check #1' \
-	'^error: char.*: could not find "tagger "$'
+	'^error:.* missingTaggerEntry:' '--no-strict'
 
 ############################################################
 # 12. tagger line label check #2
@@ -179,10 +274,10 @@ This is filler
 EOF
 
 check_verify_failure '"tagger" line label check #2' \
-	'^error: char.*: could not find "tagger "$'
+	'^error:.* missingTaggerEntry:' '--no-strict'
 
 ############################################################
-# 13. disallow missing tag author name
+# 13. allow missing tag author name like fsck
 
 cat >tag.sig <<EOF
 object $head
@@ -193,8 +288,7 @@ tagger  <> 0 +0000
 This is filler
 EOF
 
-check_verify_failure 'disallow missing tag author name' \
-	'^error: char.*: missing tagger name$'
+test_expect_mktag_success 'allow missing tag author name'
 
 ############################################################
 # 14. disallow missing tag author name
@@ -209,7 +303,7 @@ tagger T A Gger <
 EOF
 
 check_verify_failure 'disallow malformed tagger' \
-	'^error: char.*: malformed tagger field$'
+	'^error:.* badEmail:' '--no-strict'
 
 ############################################################
 # 15. allow empty tag email
@@ -222,12 +316,10 @@ tagger T A Gger <> 0 +0000
 
 EOF
 
-test_expect_success \
-    'allow empty tag email' \
-    'git mktag <tag.sig >.git/refs/tags/mytag 2>message'
+test_expect_mktag_success 'allow empty tag email'
 
 ############################################################
-# 16. disallow spaces in tag email
+# 16. allow spaces in tag email like fsck
 
 cat >tag.sig <<EOF
 object $head
@@ -237,8 +329,7 @@ tagger T A Gger <tag ger@example.com> 0 +0000
 
 EOF
 
-check_verify_failure 'disallow spaces in tag email' \
-	'^error: char.*: malformed tagger field$'
+test_expect_mktag_success 'allow spaces in tag email like fsck'
 
 ############################################################
 # 17. disallow missing tag timestamp
@@ -252,7 +343,7 @@ tagger T A Gger <tagger@example.com>__
 EOF
 
 check_verify_failure 'disallow missing tag timestamp' \
-	'^error: char.*: missing tag timestamp$'
+	'^error:.* badDate:'
 
 ############################################################
 # 18. detect invalid tag timestamp1
@@ -266,7 +357,7 @@ tagger T A Gger <tagger@example.com> Tue Mar 25 15:47:44 2008
 EOF
 
 check_verify_failure 'detect invalid tag timestamp1' \
-	'^error: char.*: missing tag timestamp$'
+	'^error:.* badDate:'
 
 ############################################################
 # 19. detect invalid tag timestamp2
@@ -280,7 +371,7 @@ tagger T A Gger <tagger@example.com> 2008-03-31T12:20:15-0500
 EOF
 
 check_verify_failure 'detect invalid tag timestamp2' \
-	'^error: char.*: malformed tag timestamp$'
+	'^error:.* badDate:'
 
 ############################################################
 # 20. detect invalid tag timezone1
@@ -294,7 +385,7 @@ tagger T A Gger <tagger@example.com> 1206478233 GMT
 EOF
 
 check_verify_failure 'detect invalid tag timezone1' \
-	'^error: char.*: malformed tag timezone$'
+	'^error:.* badTimezone:'
 
 ############################################################
 # 21. detect invalid tag timezone2
@@ -308,10 +399,10 @@ tagger T A Gger <tagger@example.com> 1206478233 +  30
 EOF
 
 check_verify_failure 'detect invalid tag timezone2' \
-	'^error: char.*: malformed tag timezone$'
+	'^error:.* badTimezone:'
 
 ############################################################
-# 22. detect invalid tag timezone3
+# 22. allow invalid tag timezone3 (the maximum is -1200/+1400)
 
 cat >tag.sig <<EOF
 object $head
@@ -321,8 +412,7 @@ tagger T A Gger <tagger@example.com> 1206478233 -1430
 
 EOF
 
-check_verify_failure 'detect invalid tag timezone3' \
-	'^error: char.*: malformed tag timezone$'
+test_expect_mktag_success 'allow invalid tag timezone'
 
 ############################################################
 # 23. detect invalid header entry
@@ -337,10 +427,41 @@ this line should not be here
 EOF
 
 check_verify_failure 'detect invalid header entry' \
-	'^error: char.*: trailing garbage in tag header$'
+	'^error:.* extraHeaderEntry:' '--no-strict'
 
-############################################################
-# 24. create valid tag
+test_expect_success 'invalid header entry config & fsck' '
+	test_must_fail git mktag <tag.sig &&
+	git mktag --no-strict <tag.sig &&
+
+	test_must_fail git -c fsck.extraHeaderEntry=error mktag <tag.sig &&
+	test_must_fail git -c fsck.extraHeaderEntry=error mktag --no-strict <tag.sig &&
+
+	test_must_fail git -c fsck.extraHeaderEntry=warn mktag <tag.sig &&
+	git -c fsck.extraHeaderEntry=warn mktag --no-strict <tag.sig &&
+
+	git -c fsck.extraHeaderEntry=ignore mktag <tag.sig &&
+	git -c fsck.extraHeaderEntry=ignore mktag --no-strict <tag.sig &&
+
+	git fsck &&
+	env GIT_TEST_GETTEXT_POISON=false \
+		git -c fsck.extraHeaderEntry=warn fsck 2>err &&
+	grep "warning .*extraHeaderEntry:" err &&
+	test_must_fail env GIT_TEST_GETTEXT_POISON=false \
+		git -c fsck.extraHeaderEntry=error 2>err fsck &&
+	grep "error .* extraHeaderEntry:" err
+'
+
+cat >tag.sig <<EOF
+object $head
+type commit
+tag mytag
+tagger T A Gger <tagger@example.com> 1206478233 -0500
+
+
+this line comes after an extra newline
+EOF
+
+test_expect_mktag_success 'allow extra newlines at start of body'
 
 cat >tag.sig <<EOF
 object $head
@@ -350,16 +471,27 @@ tagger T A Gger <tagger@example.com> 1206478233 -0500
 
 EOF
 
-test_expect_success \
-    'create valid tag' \
-    'git mktag <tag.sig >.git/refs/tags/mytag 2>message'
+test_expect_mktag_success 'allow a blank line before an empty body (1)'
+
+cat >tag.sig <<EOF
+object $head
+type commit
+tag mytag
+tagger T A Gger <tagger@example.com> 1206478233 -0500
+EOF
+
+test_expect_mktag_success 'allow no blank line before an empty body (2)'
 
 ############################################################
-# 25. check mytag
+# 24. create valid tag
 
-test_expect_success \
-    'check mytag' \
-    'git tag -l | grep mytag'
+cat >tag.sig <<EOF
+object $head
+type commit
+tag mytag
+tagger T A Gger <tagger@example.com> 1206478233 -0500
+EOF
 
+test_expect_mktag_success 'create valid tag object'
 
 test_done
diff --git a/t/t6050-replace.sh b/t/t6050-replace.sh
index c80dc10b8f..0dbe086118 100755
--- a/t/t6050-replace.sh
+++ b/t/t6050-replace.sh
@@ -129,7 +129,7 @@ tagger T A Gger <> 0 +0000
 EOF
 
 test_expect_success 'tag replaced commit' '
-     git mktag <tag.sig >.git/refs/tags/mytag 2>message
+     git mktag <tag.sig >.git/refs/tags/mytag
 '
 
 test_expect_success '"git fsck" works' '