diff --git a/src/read_config_lex.l b/src/read_config_lex.l
index eb3368a..7daaeab 100644
--- a/src/read_config_lex.l
+++ b/src/read_config_lex.l
@@ -19,6 +19,8 @@
  * Description: configuration file syntax
  */
 
+#include <string.h>
+
 #include "read_config_yy.h"
 %}