diff --git a/src/interpret.ml b/src/interpret.ml
index 2ce50db2f6468ceadfb8ec9c48642d8b6784d087..339500e2f82ea0ee73af4cd50f22d3b329ff9d44 100644
--- a/src/interpret.ml
+++ b/src/interpret.ml
@@ -497,7 +497,7 @@ let read_messages filename : run or_comment list =
         match SentenceParser.entry SentenceLexer.lex lexbuf with
         | exception Parsing.Parse_error ->
             Error.error
-              (Positions.one (Lexing.lexeme_start_p lexbuf))
+              [Positions.cpos lexbuf]
               "ill-formed sentence."
         | sentences ->
             (* In principle, we should now find a segment of whitespace