diff --git a/c/vrefbuffer.c b/c/vrefbuffer.c
index bbaf61d7..2bf97afe 100644
--- a/c/vrefbuffer.c
+++ b/c/vrefbuffer.c
@@ -77,7 +77,7 @@ int msgpack_vrefbuffer_append_ref(msgpack_vrefbuffer* vbuf,
 		const char* buf, unsigned int len)
 {
 	if(vbuf->tail == vbuf->end) {
-		const size_t nused = vbuf->end - vbuf->array;
+		const size_t nused = vbuf->tail - vbuf->array;
 		const size_t nnext = nused * 2;
 
 		struct iovec* nvec = (struct iovec*)realloc(
@@ -133,3 +133,30 @@ int msgpack_vrefbuffer_append_copy(msgpack_vrefbuffer* vbuf,
 	}
 }
 
+int msgpack_vrefbuffer_migrate(msgpack_vrefbuffer* vbuf, msgpack_vrefbuffer* to)
+{
+	const size_t tosize = to->tail - to->array;
+	if(vbuf->tail + tosize < vbuf->end) {
+		const size_t nused = vbuf->tail - vbuf->array;
+		const size_t nsize = vbuf->end  - vbuf->array;
+		const size_t reqsize = nused + tosize;
+		size_t nnext = nsize * 2;
+		while(nnext < reqsize) {
+			nnext *= 2;
+		}
+
+		struct iovec* nvec = (struct iovec*)realloc(
+				vbuf->array, sizeof(struct iovec)*nnext);
+		if(nvec == NULL) {
+			return -1;
+		}
+
+		vbuf->array = nvec;
+		vbuf->end   = nvec + nnext;
+		vbuf->tail  = nvec + nused;
+	}
+
+	memcpy(vbuf->tail, vbuf->array, sizeof(struct iovec)*tosize);
+	return 0;
+}
+
diff --git a/c/vrefbuffer.h b/c/vrefbuffer.h
index 063075f8..9f24f14f 100644
--- a/c/vrefbuffer.h
+++ b/c/vrefbuffer.h
@@ -76,6 +76,7 @@ int msgpack_vrefbuffer_append_copy(msgpack_vrefbuffer* vbuf,
 int msgpack_vrefbuffer_append_ref(msgpack_vrefbuffer* vbuf,
 		const char* buf, unsigned int len);
 
+int msgpack_vrefbuffer_migrate(msgpack_vrefbuffer* vbuf, msgpack_vrefbuffer* to);
 
 int msgpack_vrefbuffer_write(void* data, const char* buf, unsigned int len)
 {
diff --git a/cpp/vrefbuffer.hpp b/cpp/vrefbuffer.hpp
index 549d77fc..c8eca7b6 100644
--- a/cpp/vrefbuffer.hpp
+++ b/cpp/vrefbuffer.hpp
@@ -71,6 +71,13 @@ public:
 		return msgpack_vrefbuffer_veclen(this);
 	}
 
+	void migrate(vrefbuffer* to)
+	{
+		if(msgpack_vrefbuffer_migrate(this, to) < 0) {
+			throw std::bad_alloc();
+		}
+	}
+
 private:
 	typedef msgpack_vrefbuffer base;