diff --git a/core/net/rime/timesynch.c b/core/net/rime/timesynch.c
index 83ca2fd30..5a184ce6b 100644
--- a/core/net/rime/timesynch.c
+++ b/core/net/rime/timesynch.c
@@ -48,6 +48,7 @@
 #include "lib/random.h"
 #include "net/rime.h"
 #include "net/rime/timesynch.h"
+#include <string.h>
 
 #if TIMESYNCH_CONF_ENABLED
 static int authority_level;