diff --git a/tests/webtbs/tw2540.pp b/tests/webtbs/tw2540.pp
new file mode 100644
index 0000000000..b5ea5c0ba2
--- /dev/null
+++ b/tests/webtbs/tw2540.pp
@@ -0,0 +1,19 @@
+var
+  C : Char;
+  S : AnsiString;
+begin
+  S := '';
+  SetLength(S,1);
+  S[1] := '?';
+  SetLength(S,2);
+  S[2] := '?';
+  if (s <> '??') then
+    halt(1);
+
+  S := '';
+  S := S + '?';
+  S := S + '?';
+  if (s <> '??') then
+    halt(1);
+end.
+