diff --git a/src/sixlowpan/helper/sixlowpan-helper.h b/src/sixlowpan/helper/sixlowpan-helper.h
index 5785821fa..87af498f7 100644
--- a/src/sixlowpan/helper/sixlowpan-helper.h
+++ b/src/sixlowpan/helper/sixlowpan-helper.h
@@ -29,6 +29,7 @@ namespace ns3 {
 
 class Node;
 class AttributeValue;
+class Time;
 
 /**
  * \ingroup sixlowpan