diff --git a/rtl/inc/isotmp.inc b/rtl/inc/isotmp.inc
index 4d8376bb57..1948566697 100644
--- a/rtl/inc/isotmp.inc
+++ b/rtl/inc/isotmp.inc
@@ -24,7 +24,7 @@
         unique : Boolean;
       begin
         InternalChangeCase := S;
-        if Length(InternalChangeCase) then
+        if Length(InternalChangeCase)=0 then
           exit;
         unique := false;
         p := PWideChar(InternalChangeCase);