diff --git a/core/net/mac/contikimac/contikimac-framer.c b/core/net/mac/contikimac/contikimac-framer.c
index 86121df5e..cbe4c8f5f 100644
--- a/core/net/mac/contikimac/contikimac-framer.c
+++ b/core/net/mac/contikimac/contikimac-framer.c
@@ -78,6 +78,12 @@ struct hdr {
   uint8_t len;
 };
 
+/*---------------------------------------------------------------------------*/
+static int
+hdr_length(void)
+{
+  return DECORATED_FRAMER.length() + sizeof(struct hdr);
+}
 /*---------------------------------------------------------------------------*/
 static int
 create(void)
@@ -172,6 +178,7 @@ parse(void)
 }
 /*---------------------------------------------------------------------------*/
 const struct framer contikimac_framer = {
+  hdr_length,
   create,
   create_and_secure,
   parse