diff --git a/libcpp/directives.cc b/libcpp/directives.cc
index 95095b08eafe..9c906b390660 100644
--- a/libcpp/directives.cc
+++ b/libcpp/directives.cc
@@ -2075,7 +2075,7 @@ do_pragma_once (cpp_reader *pfile)
 {
   if (_cpp_in_main_source_file (pfile))
     cpp_warning (pfile, CPP_W_PRAGMA_ONCE_OUTSIDE_HEADER,
-		 "%<#pragma once%> in main file");
+		 "'#pragma once' in main file");
 
   check_eol (pfile, false);
   _cpp_mark_file_once_only (pfile, pfile->buffer->file);