diff --git a/scripts/kconfig/zconf.l b/scripts/kconfig/zconf.l
index 200a3fe..642f5b2 100644
--- a/scripts/kconfig/zconf.l
+++ b/scripts/kconfig/zconf.l
@@ -106,7 +106,11 @@ n	[A-Za-z0-9_]
 		zconflval.string = text;
 		return T_WORD;
 	}
-	.
+	.	{
+		fprintf(stderr,
+		        "%s:%d:warning: ignoring unsupported character '%c'\n",
+		        zconf_curname(), zconf_lineno(), *yytext);
+	}
 	\n	{
 		BEGIN(INITIAL);
 		current_file->lineno++;