diff --git a/lib/postgrex/protocol.ex b/lib/postgrex/protocol.ex
index 3afcf902..f446d93e 100644
--- a/lib/postgrex/protocol.ex
+++ b/lib/postgrex/protocol.ex
@@ -403,6 +403,7 @@ defmodule Postgrex.Protocol do
           | {:disconnect, %DBConnection.ConnectionError{}, state}
   def handle_execute(%Query{} = query, params, opts, s) do
     comment = Keyword.get(opts, :comment)
+    validate_comment(query.comment, s)
     query = %{query | comment: comment}
 
     case Keyword.get(opts, :postgrex_copy, false) do