diff --git a/src/scan.l b/src/scan.l
index b14ce18e..7e7e4700 100644
--- a/src/scan.l
+++ b/src/scan.l
@@ -3,6 +3,10 @@
 #include <string.h>
 
 #include "picrin.h"
+
+/* Guts! bison3 seems emit prototype declaration of yyparse in y.tab.h... */
+struct parser_control;
+
 #include "y.tab.h"
 
 #define YY_DECL int yylex_(YYSTYPE *yylvalp, yyscan_t yyscanner)