diff --git a/src/scan.l b/src/scan.l
index b14ce18e..2b7de9e5 100644
--- a/src/scan.l
+++ b/src/scan.l
@@ -5,6 +5,8 @@
 #include "picrin.h"
 #include "y.tab.h"
 
+struct parser_control;
+
 #define YY_DECL int yylex_(YYSTYPE *yylvalp, yyscan_t yyscanner)
 %}