diff --git a/src/libcharon/plugins/lookip/lookip.c b/src/libcharon/plugins/lookip/lookip.c
index 67a19300f..b42004abd 100644
--- a/src/libcharon/plugins/lookip/lookip.c
+++ b/src/libcharon/plugins/lookip/lookip.c
@@ -22,6 +22,7 @@
 #include <stddef.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 #include <errno.h>
 #include <getopt.h>
 #include <arpa/inet.h>