diff --git a/pb.c b/pb.c
index 34bf59c..6d8a777 100755
--- a/pb.c
+++ b/pb.c
@@ -1728,7 +1728,7 @@ static void lpb_encode_onefield(lpb_Env *e, const pb_Type *t, const pb_Field *f,
     else if (f->repeated)
         lpbE_repeated(e, f, idx);
     else if (!f->type || !f->type->is_dead)
-        lpbE_tagfield(e, f, t->is_proto3 && !f->oneof_idx, idx);
+        lpbE_tagfield(e, f, t->is_proto3 && !f->oneof_idx && f->type_id != PB_Tmessage, idx);
 }
 
 static void lpbE_encode(lpb_Env *e, const pb_Type *t, int idx) {