diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 27f6672589ce2..7832b20baac2e 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -758,11 +758,17 @@ static bool mptcp_skb_can_collapse_to(u64 write_seq,
 	return mpext && mpext->data_seq + mpext->data_len == write_seq;
 }
 
+/* we can append data to the given data frag if:
+ * - there is space available in the backing page_frag
+ * - the data frag tail matches the current page_frag free offset
+ * - the data frag end sequence number matches the current write seq
+ */
 static bool mptcp_frag_can_collapse_to(const struct mptcp_sock *msk,
 				       const struct page_frag *pfrag,
 				       const struct mptcp_data_frag *df)
 {
 	return df && pfrag->page == df->page &&
+		pfrag->offset == (df->offset + df->data_len) &&
 		df->data_seq + df->data_len == msk->write_seq;
 }