diff --git a/ide/packages/idedebugger/idedebuggerwatchresutils.pas b/ide/packages/idedebugger/idedebuggerwatchresutils.pas
index add337111e..f91970b376 100644
--- a/ide/packages/idedebugger/idedebuggerwatchresutils.pas
+++ b/ide/packages/idedebugger/idedebuggerwatchresutils.pas
@@ -577,10 +577,13 @@ function TStringBuilderPart.GetFullString: String;
 var
   p: PChar;
 begin
+  Result := '';
   if FData = nil then
-    exit('');
+    exit();
   if FType = sbfString then
     exit(string(FData));
+  if PHeader(FData)^.FTotalLen = 0 then
+    exit;
 
   SetLength(Result, PHeader(FData)^.FTotalLen);
   p := pchar(Result);