diff --git a/source/main.pas b/source/main.pas
index 5278a7f0..5f6ac0b8 100644
--- a/source/main.pas
+++ b/source/main.pas
@@ -6695,7 +6695,8 @@ var
   Proposal: TSynCompletionProposal;
 begin
   Proposal := Sender as TSynCompletionProposal;
-  Proposal.Title := Proposal.InsertItem(AIndex);
+  if (AIndex >= 0) and (AIndex < Proposal.ItemList.Count) then
+    Proposal.Title := Proposal.InsertItem(AIndex);
 end;