diff --git a/src/parse.y b/src/parse.y
index 75cc11a1..e30b3e3c 100644
--- a/src/parse.y
+++ b/src/parse.y
@@ -9,8 +9,6 @@ struct parser_control {
   pic_value value;
 };
 
-#define YYDEBUG 1
-
 %}
 
 %parse-param {struct parser_control *p}
diff --git a/src/scan.l b/src/scan.l
index 4071eee8..a3300a0e 100644
--- a/src/scan.l
+++ b/src/scan.l
@@ -12,6 +12,8 @@ struct parser_control {
 #define YY_DECL int yylex (struct parser_control *p)
 %}
 
+%option nounput
+
 %%
 
 [ \t\n\r]	/* skip whitespace */
diff --git a/src/value.c b/src/value.c
index 2233fb95..fe8c996e 100644
--- a/src/value.c
+++ b/src/value.c
@@ -1,3 +1,5 @@
+#include <stdlib.h>
+
 #include "picrin.h"
 
 enum pic_tt