diff --git a/include/libwebsockets/lws-write.h b/include/libwebsockets/lws-write.h
index b73e51c78..6e0be6b34 100644
--- a/include/libwebsockets/lws-write.h
+++ b/include/libwebsockets/lws-write.h
@@ -123,6 +123,7 @@ struct lws_write_passthru {
 
 /**
  * lws_write() - Apply protocol then write data to client
+ *
  * \param wsi:	Websocket instance (available from user callback)
  * \param buf:	The data to send.  For data being sent on a websocket
  *		connection (ie, not default http), this buffer MUST have
@@ -216,7 +217,17 @@ lws_write(struct lws *wsi, unsigned char *buf, size_t len,
 #define lws_write_http(wsi, buf, len) \
 	lws_write(wsi, (unsigned char *)(buf), len, LWS_WRITE_HTTP)
 
-/* helper for multi-frame ws message flags */
+/**
+ * lws_write_ws_flags() - Helper for multi-frame ws message flags
+ *
+ * \param initial: the lws_write flag to use for the start fragment, eg,
+ *		   LWS_WRITE_TEXT
+ * \param is_start: nonzero if this is the first fragment of the message
+ * \param is_end: nonzero if this is the last fragment of the message
+ *
+ * Returns the correct LWS_WRITE_ flag to use for each fragment of a message
+ * in turn.
+ */
 static LWS_INLINE int
 lws_write_ws_flags(int initial, int is_start, int is_end)
 {
@@ -232,4 +243,21 @@ lws_write_ws_flags(int initial, int is_start, int is_end)
 
 	return r;
 }
+
+/**
+ * lws_raw_transaction_completed() - Helper for flushing before close
+ *
+ * \param wsi: the struct lws to operate on
+ *
+ * Returns -1 if the wsi can close now.  However if there is buffered, unsent
+ * data, the wsi is marked as to be closed when the output buffer data is
+ * drained, and it returns 0.
+ *
+ * For raw cases where the transaction completed without failure,
+ * `return lws_raw_transaction_completed(wsi)` should better be used than
+ * return -1.
+ */
+LWS_VISIBLE int LWS_WARN_UNUSED_RESULT
+lws_raw_transaction_completed(struct lws *wsi);
+
 ///@}
diff --git a/lib/core/libwebsockets.c b/lib/core/libwebsockets.c
index 661493c51..35218a385 100644
--- a/lib/core/libwebsockets.c
+++ b/lib/core/libwebsockets.c
@@ -1437,6 +1437,29 @@ lws_get_network_wsi(struct lws *wsi)
 	return wsi;
 }
 
+
+LWS_VISIBLE int LWS_WARN_UNUSED_RESULT
+lws_raw_transaction_completed(struct lws *wsi)
+{
+	if (lws_has_buffered_out(wsi)) {
+		/*
+		 * ...so he tried to send something large, but it went out
+		 * as a partial, but he immediately called us to say he wants
+		 * to close the connection.
+		 *
+		 * Defer the close until the last part of the partial is sent.
+		 *
+		 */
+		lwsl_debug("%s: %p: deferring due to partial\n", __func__, wsi);
+		wsi->close_when_buffered_out_drained = 1;
+		lws_callback_on_writable(wsi);
+
+		return 0;
+	}
+
+	return -1;
+}
+
 LWS_VISIBLE LWS_EXTERN const struct lws_protocols *
 lws_vhost_name_to_protocol(struct lws_vhost *vh, const char *name)
 {
diff --git a/lib/core/output.c b/lib/core/output.c
index 49d289db4..e58aa45b2 100644
--- a/lib/core/output.c
+++ b/lib/core/output.c
@@ -150,6 +150,11 @@ int lws_issue_raw(struct lws *wsi, unsigned char *buf, size_t len)
 				return -1; /* retry closing now */
 			}
 
+			if (wsi->close_when_buffered_out_drained) {
+				wsi->close_when_buffered_out_drained = 0;
+				return -1;
+			}
+
 #if defined(LWS_ROLE_H1) || defined(LWS_ROLE_H2)
 #if !defined(LWS_WITHOUT_SERVER)
 			if (wsi->http.deferred_transaction_completed) {
diff --git a/lib/core/private.h b/lib/core/private.h
index 295f27d51..9a8dc8684 100644
--- a/lib/core/private.h
+++ b/lib/core/private.h
@@ -980,6 +980,7 @@ struct lws {
 	unsigned int handling_404:1;
 	unsigned int protocol_bind_balance:1;
 	unsigned int unix_skt:1;
+	unsigned int close_when_buffered_out_drained:1;
 
 	unsigned int could_have_pending:1; /* detect back-to-back writes */
 	unsigned int outer_will_close:1;