diff --git a/src/libcharon/plugins/load_tester/load_tester.c b/src/libcharon/plugins/load_tester/load_tester.c
index b7b971ee8..f5a998ecc 100644
--- a/src/libcharon/plugins/load_tester/load_tester.c
+++ b/src/libcharon/plugins/load_tester/load_tester.c
@@ -21,6 +21,7 @@
 #include <stddef.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 #include <errno.h>
 
 /**