diff --git a/lustre/tests/sanityn.sh b/lustre/tests/sanityn.sh
index 918dbac5b5..b44502e31c 100755
--- a/lustre/tests/sanityn.sh
+++ b/lustre/tests/sanityn.sh
@@ -746,6 +746,25 @@ test_26b() {
 }
 run_test 26b "sync mtime between ost and mds"
 
+test_26c() {
+	multiop_bg_pause $DIR1/$tfile O_c || return 1
+	MULTIPID=$!
+	echo
+	echo "--- set-in-past on opened file"
+	touch -m -d @978261179 $DIR2/$tfile
+	kill -USR1 $MULTIPID
+	wait $MULTIPID || error "wait for PID $MULTIPID failed"
+	stat $DIR1/$tfile | grep -e "File" -e "Modify"
+	stat $DIR2/$tfile | grep -e "File" -e "Modify"
+
+	echo
+	echo "--- set-in-past on closed file"
+	touch -m -d @978261179 $DIR2/$tfile
+	stat $DIR1/$tfile | grep -e "File" -e "Modify"
+	stat $DIR2/$tfile | grep -e "File" -e "Modify"
+}
+run_test 26c "allow mtime to get older while file is open"
+
 test_27() {
 	cancel_lru_locks $OSC
 	lctl clear