diff --git a/builtin-tag.c b/builtin-tag.c
index 517419fd3d..274901a408 100644
--- a/builtin-tag.c
+++ b/builtin-tag.c
@@ -236,14 +236,18 @@ static const char tag_template[] =
 	"# Write a tag message\n"
 	"#\n";
 
+static void set_signingkey(const char *value)
+{
+	if (strlcpy(signingkey, value, sizeof(signingkey)) >= sizeof(signingkey))
+		die("signing key value too long (%.10s...)", value);
+}
+
 static int git_tag_config(const char *var, const char *value)
 {
 	if (!strcmp(var, "user.signingkey")) {
 		if (!value)
 			die("user.signingkey without value");
-		if (strlcpy(signingkey, value, sizeof(signingkey))
-						>= sizeof(signingkey))
-			die("user.signingkey value too long");
+		set_signingkey(value);
 		return 0;
 	}
 
@@ -396,6 +400,10 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
 
 	argc = parse_options(argc, argv, options, git_tag_usage, 0);
 
+	if (keyid) {
+		sign = 1;
+		set_signingkey(keyid);
+	}
 	if (sign)
 		annotate = 1;
 
diff --git a/t/t7004-tag.sh b/t/t7004-tag.sh
index c7130c4dcc..09d56e0839 100755
--- a/t/t7004-tag.sh
+++ b/t/t7004-tag.sh
@@ -640,6 +640,46 @@ test_expect_success 'creating a signed tag with -m message should succeed' '
 	git diff expect actual
 '
 
+get_tag_header u-signed-tag $commit commit $time >expect
+echo 'Another message' >>expect
+echo '-----BEGIN PGP SIGNATURE-----' >>expect
+test_expect_success 'sign with a given key id' '
+
+	git tag -u committer@example.com -m "Another message" u-signed-tag &&
+	get_tag_msg u-signed-tag >actual &&
+	git diff expect actual
+
+'
+
+test_expect_success 'sign with an unknown id (1)' '
+
+	! git tag -u author@example.com -m "Another message" o-signed-tag
+
+'
+
+test_expect_success 'sign with an unknown id (2)' '
+
+	! git tag -u DEADBEEF -m "Another message" o-signed-tag
+
+'
+
+cat >fakeeditor <<'EOF'
+#!/bin/sh
+test -n "$1" && exec >"$1"
+echo A signed tag message
+echo from a fake editor.
+EOF
+chmod +x fakeeditor
+
+get_tag_header implied-sign $commit commit $time >expect
+./fakeeditor >>expect
+echo '-----BEGIN PGP SIGNATURE-----' >>expect
+test_expect_success '-u implies signed tag' '
+	GIT_EDITOR=./fakeeditor git-tag -u CDDE430D implied-sign &&
+	get_tag_msg implied-sign >actual &&
+	git diff expect actual
+'
+
 cat >sigmsgfile <<EOF
 Another signed tag
 message in a file.
@@ -667,13 +707,6 @@ test_expect_success 'creating a signed tag with -F - should succeed' '
 	git diff expect actual
 '
 
-cat >fakeeditor <<'EOF'
-#!/bin/sh
-test -n "$1" && exec >"$1"
-echo A signed tag message
-echo from a fake editor.
-EOF
-chmod +x fakeeditor
 get_tag_header implied-annotate $commit commit $time >expect
 ./fakeeditor >>expect
 echo '-----BEGIN PGP SIGNATURE-----' >>expect