diff --git a/compiler/dbgbase.pas b/compiler/dbgbase.pas
index 18eaf2e35a..0172e3b576 100644
--- a/compiler/dbgbase.pas
+++ b/compiler/dbgbase.pas
@@ -339,6 +339,8 @@ implementation
                     internalerror(200610054);
                 end;
               end;
+            if looplist.count=deftowritelist.count then
+              internalerror(2018011401);
             looplist.clear;
             templist := looplist;
             looplist := deftowritelist;