diff --git a/udfs/sql_printf.cc b/udfs/sql_printf.cc
index 1890fc3..2270268 100644
--- a/udfs/sql_printf.cc
+++ b/udfs/sql_printf.cc
@@ -1,6 +1,7 @@
 
 #include <stdio.h>
 #include <string.h>
+#include <stdlib.h>
 #include <mysql/mysql.h>
 
 #define NAME        "sql_printf"