diff --git a/string/test-strncmp.c b/string/test-strncmp.c
index df7cea4068..1a87f0e73e 100644
--- a/string/test-strncmp.c
+++ b/string/test-strncmp.c
@@ -445,6 +445,18 @@ check4 (void)
   check_result (impl, s1, s2, size, exp_result);
 }
 
+static void
+check5 (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);
+}
+
 static void
 check_overflow (void)
 {
@@ -569,6 +581,7 @@ test_main (void)
   check2 ();
   check3 ();
   check4 ();
+  check5 ();
 
   printf ("%23s", "");
   FOR_EACH_IMPL (impl, 0)