diff --git a/tests/tbf/tb0161.pp b/tests/tbf/tb0161.pp
new file mode 100644
index 0000000000..2c410e7629
--- /dev/null
+++ b/tests/tbf/tb0161.pp
@@ -0,0 +1,20 @@
+{ %fail }
+
+uses Strings;
+
+Function PosEx(const SubStr, S: string; Offset: Cardinal): Integer;
+
+var i : pchar;
+begin
+  if (offset<1) or (offset>length(s)) then exit(0);
+  i:=strpos(@s[1],@substr[offset]);
+  if i=nil then
+    PosEx:=0
+  else
+  // This should be forbidden
+    PosEx:=(i-s)+offset;
+end;
+
+begin
+end.
+