diff --git a/components/codetools/sourcelog.pas b/components/codetools/sourcelog.pas
index 26fd76d151..fdf65336e3 100644
--- a/components/codetools/sourcelog.pas
+++ b/components/codetools/sourcelog.pas
@@ -645,7 +645,7 @@ begin
     ReAllocMem(FLineRanges,0);
     exit;
   end;
-  Cap:=length(FSource) div 20+100;
+  Cap:=FSrcLen div 20+100;
   ReAllocMem(FLineRanges,Cap*SizeOf(TLineRange));
   line:=0;
   FLineRanges[line].StartPos:=1;