diff --git a/drivers/network/afd/afd/lock.c b/drivers/network/afd/afd/lock.c
index 4036a9c9ee0..1c7f5e2c63e 100644
--- a/drivers/network/afd/afd/lock.c
+++ b/drivers/network/afd/afd/lock.c
@@ -116,6 +116,7 @@ VOID UnlockBuffers( PAFD_WSABUF Buf, UINT Count, BOOL Address ) {
 	if( Map[i].Mdl ) {
 	    MmUnlockPages( Map[i].Mdl );
 	    IoFreeMdl( Map[i].Mdl );
+	    Map[i].Mdl = NULL;
 	}
     }