diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index 3d4ab929f91..04aa770d981 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -209,6 +209,13 @@ static bool waiting_for_ping_response = false;
 /* Timestamp when walsender received the shutdown request */
 static TimestampTz shutdown_request_timestamp = 0;
 
+/*
+ * Set after queueing the CommandComplete message that ends WAL streaming
+ * during shutdown. This prevents WalSndDone() and WalSndDoneImmediate()
+ * from queueing the same message twice.
+ */
+static bool shutdown_stream_done_queued = false;
+
 /*
  * While streaming WAL in Copy mode, streamingDoneSending is set to true
  * after we have sent CopyDone. We should not send any more CopyData messages
@@ -3713,15 +3720,17 @@ WalSndDoneImmediate(void)
 {
 	WalSndState state = MyWalSnd->state;
 
-	if (state == WALSNDSTATE_CATCHUP ||
-		state == WALSNDSTATE_STREAMING ||
-		state == WALSNDSTATE_STOPPING)
+	if ((state == WALSNDSTATE_CATCHUP ||
+		 state == WALSNDSTATE_STREAMING ||
+		 state == WALSNDSTATE_STOPPING) &&
+		!shutdown_stream_done_queued)
 	{
 		QueryCompletion qc;
 
 		/* Try to inform receiver that XLOG streaming is done */
 		SetQueryCompletion(&qc, CMDTAG_COPY, 0);
-		EndCommand(&qc, DestRemote, false);
+		EndCommandExtended(&qc, DestRemote, false, true);
+		shutdown_stream_done_queued = true;
 
 		/*
 		 * Note that the output buffer may be full during the forced shutdown
@@ -3778,10 +3787,55 @@ WalSndDone(WalSndSendDataCallback send_data)
 	{
 		QueryCompletion qc;
 
+		Assert(!shutdown_stream_done_queued);
+
 		/* Inform the standby that XLOG streaming is done */
 		SetQueryCompletion(&qc, CMDTAG_COPY, 0);
-		EndCommand(&qc, DestRemote, false);
-		pq_flush();
+		EndCommandExtended(&qc, DestRemote, false, true);
+		shutdown_stream_done_queued = true;
+
+		/*
+		 * Reset last_reply_timestamp so subsequent WalSndComputeSleeptime()
+		 * calls ignore wal_sender_timeout during shutdown.
+		 */
+		last_reply_timestamp = 0;
+
+		/*
+		 * Do not call pq_flush() here, since it can block indefinitely while
+		 * waiting for the socket to become writable, preventing
+		 * wal_sender_shutdown_timeout from being enforced. Instead, use the
+		 * walsender nonblocking flush path so the shutdown timeout continues
+		 * to be checked while the send buffer drains.
+		 */
+		for (;;)
+		{
+			long		sleeptime;
+
+			/*
+			 * During shutdown, die if the shutdown timeout expires. Call this
+			 * before WalSndComputeSleeptime() so the timeout is considered
+			 * when computing sleep time.
+			 */
+			WalSndCheckShutdownTimeout();
+
+			if (!pq_is_send_pending())
+				break;
+
+			sleeptime = WalSndComputeSleeptime(GetCurrentTimestamp());
+
+			/* Sleep until something happens or we time out */
+			WalSndWait(WL_SOCKET_WRITEABLE, sleeptime,
+					   WAIT_EVENT_WAL_SENDER_WRITE_DATA);
+
+			/* Clear any already-pending wakeups */
+			ResetLatch(MyLatch);
+
+			CHECK_FOR_INTERRUPTS();
+
+			/* Try to flush pending output to the client */
+			if (pq_flush_if_writable() != 0)
+				WalSndShutdown();
+		}
 
 		proc_exit(0);
 	}
diff --git a/src/backend/tcop/dest.c b/src/backend/tcop/dest.c
index fb163930c89..bdc3dad3357 100644
--- a/src/backend/tcop/dest.c
+++ b/src/backend/tcop/dest.c
@@ -165,8 +165,10 @@ CreateDestReceiver(CommandDest dest)
  *		EndCommand - clean up the destination at end of command
  * ----------------
  */
+
 void
-EndCommand(const QueryCompletion *qc, CommandDest dest, bool force_undecorated_output)
+EndCommandExtended(const QueryCompletion *qc, CommandDest dest,
+				   bool force_undecorated_output, bool noblock)
 {
 	char		completionTag[COMPLETION_TAG_BUFSIZE];
 	Size		len;
@@ -179,7 +181,10 @@ EndCommand(const QueryCompletion *qc, CommandDest dest, bool force_undecorated_o
 
 			len = BuildQueryCompletionString(completionTag, qc,
 											 force_undecorated_output);
-			pq_putmessage(PqMsg_CommandComplete, completionTag, len + 1);
+			if (noblock)
+				pq_putmessage_noblock(PqMsg_CommandComplete, completionTag, len + 1);
+			else
+				pq_putmessage(PqMsg_CommandComplete, completionTag, len + 1);
 			break;
 
 		case DestNone:
@@ -196,6 +201,12 @@ EndCommand(const QueryCompletion *qc, CommandDest dest, bool force_undecorated_o
 	}
 }
 
+void
+EndCommand(const QueryCompletion *qc, CommandDest dest, bool force_undecorated_output)
+{
+	EndCommandExtended(qc, dest, force_undecorated_output, false);
+}
+
 /* ----------------
  *		EndReplicationCommand - stripped down version of EndCommand
  *
diff --git a/src/include/tcop/dest.h b/src/include/tcop/dest.h
index 4e4f532d8cc..103f27fc3cb 100644
--- a/src/include/tcop/dest.h
+++ b/src/include/tcop/dest.h
@@ -136,6 +136,8 @@ extern PGDLLIMPORT DestReceiver *None_Receiver; /* permanent receiver for
 
 extern void BeginCommand(CommandTag commandTag, CommandDest dest);
 extern DestReceiver *CreateDestReceiver(CommandDest dest);
+extern void EndCommandExtended(const QueryCompletion *qc, CommandDest dest,
+							   bool force_undecorated_output, bool noblock);
 extern void EndCommand(const QueryCompletion *qc, CommandDest dest,
 					   bool force_undecorated_output);
 extern void EndReplicationCommand(const char *commandTag);