diff --git a/pkg/wakaama/contrib/lwm2m_client.c b/pkg/wakaama/contrib/lwm2m_client.c
index 8b0e05b5ab..43ff906bd0 100644
--- a/pkg/wakaama/contrib/lwm2m_client.c
+++ b/pkg/wakaama/contrib/lwm2m_client.c
@@ -21,6 +21,8 @@
 
 #include <string.h>
 
+#include "timex.h"
+
 #include "liblwm2m.h"
 
 #include "lwm2m_platform.h"