diff --git a/fsck.c b/fsck.c
index 99c0497674..760e072cce 100644
--- a/fsck.c
+++ b/fsck.c
@@ -245,6 +245,8 @@ static int fsck_tree(struct tree *item, int strict, fsck_error error_func)
 
 static int fsck_ident(char **ident, struct object *obj, fsck_error error_func)
 {
+	char *end;
+
 	if (**ident == '<')
 		return error_func(obj, FSCK_ERROR, "invalid author/committer line - missing space before email");
 	*ident += strcspn(*ident, "<>\n");
@@ -264,10 +266,11 @@ static int fsck_ident(char **ident, struct object *obj, fsck_error error_func)
 	(*ident)++;
 	if (**ident == '0' && (*ident)[1] != ' ')
 		return error_func(obj, FSCK_ERROR, "invalid author/committer line - zero-padded date");
-	*ident += strspn(*ident, "0123456789");
-	if (**ident != ' ')
+	if (strtoul(*ident, &end, 10) == ULONG_MAX)
+		return error_func(obj, FSCK_ERROR, "invalid author/committer line - date causes integer overflow");
+	if (end == *ident || *end != ' ')
 		return error_func(obj, FSCK_ERROR, "invalid author/committer line - bad date");
-	(*ident)++;
+	*ident = end + 1;
 	if ((**ident != '+' && **ident != '-') ||
 	    !isdigit((*ident)[1]) ||
 	    !isdigit((*ident)[2]) ||
@@ -287,9 +290,6 @@ static int fsck_commit(struct commit *commit, fsck_error error_func)
 	int parents = 0;
 	int err;
 
-	if (commit->date == ULONG_MAX)
-		return error_func(&commit->object, FSCK_ERROR, "invalid author/committer line");
-
 	if (memcmp(buffer, "tree ", 5))
 		return error_func(&commit->object, FSCK_ERROR, "invalid format - expected 'tree' line");
 	if (get_sha1_hex(buffer+5, tree_sha1) || buffer[45] != '\n')
diff --git a/t/t1450-fsck.sh b/t/t1450-fsck.sh
index d730734fde..8c739c9613 100755
--- a/t/t1450-fsck.sh
+++ b/t/t1450-fsck.sh
@@ -142,6 +142,20 @@ test_expect_success '> in name is reported' '
 	grep "error in commit $new" out
 '
 
+# date is 2^64 + 1
+test_expect_success 'integer overflow in timestamps is reported' '
+	git cat-file commit HEAD >basis &&
+	sed "s/^\\(author .*>\\) [0-9]*/\\1 18446744073709551617/" \
+		<basis >bad-timestamp &&
+	new=$(git hash-object -t commit -w --stdin <bad-timestamp) &&
+	test_when_finished "remove_object $new" &&
+	git update-ref refs/heads/bogus "$new" &&
+	test_when_finished "git update-ref -d refs/heads/bogus" &&
+	git fsck 2>out &&
+	cat out &&
+	grep "error in commit $new.*integer overflow" out
+'
+
 test_expect_success 'tag pointing to nonexistent' '
 	cat >invalid-tag <<-\EOF &&
 	object ffffffffffffffffffffffffffffffffffffffff