diff --git a/components/debuggerintf/dbgintfdebuggerbase.pp b/components/debuggerintf/dbgintfdebuggerbase.pp
index e124d93e34..d016a4dd3d 100644
--- a/components/debuggerintf/dbgintfdebuggerbase.pp
+++ b/components/debuggerintf/dbgintfdebuggerbase.pp
@@ -3304,6 +3304,8 @@ begin
   if FDataValidity = AValidity then exit;
   Old := FDataValidity;
   FDataValidity := AValidity;
+  if AValidity = ddsUnknown then
+    ClearDispValues;
   DoDataValidityChanged(Old);
 end;