diff --git a/git-commit.sh b/git-commit.sh
index 485339754c..cef76a7775 100755
--- a/git-commit.sh
+++ b/git-commit.sh
@@ -515,13 +515,16 @@ else
 	# we need to check if there is anything to commit
 	run_status >/dev/null
 fi
-if [ "$?" != "0" -a ! -f "$GIT_DIR/MERGE_HEAD" ]
-then
+case "$?,$PARENTS" in
+0,* | *,-p' '?*-p' '?*)
+	# a merge commit can record the same tree as its parent.
+	;;
+*)
 	rm -f "$GIT_DIR/COMMIT_EDITMSG" "$GIT_DIR/SQUASH_MSG"
 	use_status_color=t
 	run_status
 	exit 1
-fi
+esac
 
 case "$no_edit" in
 '')
diff --git a/t/t7501-commit.sh b/t/t7501-commit.sh
index 31a6f63399..2e7bcb016a 100755
--- a/t/t7501-commit.sh
+++ b/t/t7501-commit.sh
@@ -244,4 +244,36 @@ test_expect_success 'multiple -m' '
 
 '
 
+test_expect_success 'same tree (single parent)' '
+
+	if git commit -m empty
+	then
+		echo oops -- should have complained
+		false
+	else
+		: happy
+	fi
+
+'
+
+test_expect_success 'same tree (merge and amend merge)' '
+
+	git checkout -b side HEAD^ &&
+	echo zero >zero &&
+	git add zero &&
+	git commit -m "add zero" &&
+	git checkout master &&
+
+	git merge -s ours side -m "empty ok" &&
+	git diff HEAD^ HEAD >actual &&
+	: >expected &&
+	diff -u expected actual &&
+
+	git commit --amend -m "empty really ok" &&
+	git diff HEAD^ HEAD >actual &&
+	: >expected &&
+	diff -u expected actual
+
+'
+
 test_done