diff --git a/builtin/commit.c b/builtin/commit.c
index c5ab683d5b..58e477409c 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -455,15 +455,21 @@ static void determine_author_info(void)
 		if (!a)
 			die("invalid commit: %s", use_message);
 
-		lb = strstr(a + 8, " <");
-		rb = strstr(a + 8, "> ");
-		eol = strchr(a + 8, '\n');
-		if (!lb || !rb || !eol)
+		lb = strchrnul(a + strlen("\nauthor "), '<');
+		rb = strchrnul(lb, '>');
+		eol = strchrnul(rb, '\n');
+		if (!*lb || !*rb || !*eol)
 			die("invalid commit: %s", use_message);
 
-		name = xstrndup(a + 8, lb - (a + 8));
-		email = xstrndup(lb + 2, rb - (lb + 2));
-		date = xstrndup(rb + 2, eol - (rb + 2));
+		if (lb == a + strlen("\nauthor "))
+			/* \nauthor <foo@example.com> */
+			name = xcalloc(1, 1);
+		else
+			name = xmemdupz(a + strlen("\nauthor "),
+					(lb - strlen(" ") -
+					 (a + strlen("\nauthor "))));
+		email = xmemdupz(lb + strlen("<"), rb - (lb + strlen("<")));
+		date = xmemdupz(rb + strlen("> "), eol - (rb + strlen("> ")));
 	}
 
 	if (force_author) {
diff --git a/t/t7509-commit.sh b/t/t7509-commit.sh
index d52c060b06..3ea33db6c7 100755
--- a/t/t7509-commit.sh
+++ b/t/t7509-commit.sh
@@ -83,6 +83,52 @@ test_expect_success '--amend option copies authorship' '
 	test_cmp expect actual
 '
 
+sha1_file() {
+	echo "$*" | sed "s#..#.git/objects/&/#"
+}
+remove_object() {
+	rm -f $(sha1_file "$*")
+}
+no_reflog() {
+	cp .git/config .git/config.saved &&
+	echo "[core] logallrefupdates = false" >>.git/config &&
+	test_when_finished "mv -f .git/config.saved .git/config" &&
+
+	if test -e .git/logs
+	then
+		mv .git/logs . &&
+		test_when_finished "mv logs .git/"
+	fi
+}
+
+test_expect_success '--amend option with empty author' '
+	git cat-file commit Initial >tmp &&
+	sed "s/author [^<]* </author  </" tmp >empty-author &&
+	no_reflog &&
+	sha=$(git hash-object -t commit -w empty-author) &&
+	test_when_finished "remove_object $sha" &&
+	git checkout $sha &&
+	test_when_finished "git checkout Initial" &&
+	echo "Empty author test" >>foo &&
+	test_tick &&
+	! git commit -a -m "empty author" --amend 2>err &&
+	grep "empty ident" err
+'
+
+test_expect_success '--amend option with missing author' '
+	git cat-file commit Initial >tmp &&
+	sed "s/author [^<]* </author </" tmp >malformed &&
+	no_reflog &&
+	sha=$(git hash-object -t commit -w malformed) &&
+	test_when_finished "remove_object $sha" &&
+	git checkout $sha &&
+	test_when_finished "git checkout Initial" &&
+	echo "Missing author test" >>foo &&
+	test_tick &&
+	! git commit -a -m "malformed author" --amend 2>err &&
+	grep "empty ident" err
+'
+
 test_expect_success '--reset-author makes the commit ours even with --amend option' '
 	git checkout Initial &&
 	echo "Test 6" >>foo &&