diff --git a/src/core/mac/mac.cpp b/src/core/mac/mac.cpp
index f6236ce41..a7e1d88ec 100644
--- a/src/core/mac/mac.cpp
+++ b/src/core/mac/mac.cpp
@@ -669,6 +669,8 @@ void Mac::SentFrame(bool aAcked)
             mSendTail = NULL;
         }
 
+        sender->mNext = NULL;
+
         mDataSequence++;
         sender->HandleSentFrame(sendFrame);