diff --git a/rtl/objpas/classes/stringl.inc b/rtl/objpas/classes/stringl.inc
index 3f066391c3..a3c2495316 100644
--- a/rtl/objpas/classes/stringl.inc
+++ b/rtl/objpas/classes/stringl.inc
@@ -1390,6 +1390,8 @@ var
   CompareRes: PtrInt;
 begin
   Result := false;
+  if Not Sorted then 
+    exit;
   // Use binary search.
   L := 0;
   R := Count - 1;