diff --git a/string/test-strncmp.c b/string/test-strncmp.c
index e7d5edea39..22b7dfa73b 100644
--- a/string/test-strncmp.c
+++ b/string/test-strncmp.c
@@ -434,6 +434,18 @@ check3 (void)
 	}
 }
 
+static void
+check4 (void)
+{
+  const CHAR *s1 = L ("abc");
+  CHAR *s2 = STRDUP (s1);
+
+  FOR_EACH_IMPL (impl, 0)
+    check_result (impl, s1, s2, SIZE_MAX, 0);
+
+  free (s2);
+}
+
 int
 test_main (void)
 {
@@ -444,6 +456,7 @@ test_main (void)
   check1 ();
   check2 ();
   check3 ();
+  check4 ();
 
   printf ("%23s", "");
   FOR_EACH_IMPL (impl, 0)