Index: lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerLLGS.cpp
===================================================================
--- lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerLLGS.cpp
+++ lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerLLGS.cpp
@@ -474,6 +474,8 @@
 
   StreamGDBRemote response;
   response.Format("{0:g}", *wait_status);
+  if (bool(m_extensions_supported & NativeProcessProtocol::Extension::multiprocess))
+    response.Format(";process:{0:x-}", process->GetID());
   return SendPacketNoLock(response.GetString());
 }
 
Index: lldb/test/API/tools/lldb-server/TestGdbRemoteFork.py
===================================================================
--- lldb/test/API/tools/lldb-server/TestGdbRemoteFork.py
+++ lldb/test/API/tools/lldb-server/TestGdbRemoteFork.py
@@ -75,7 +75,7 @@
         # resume the parent
         self.test_sequence.add_log_lines([
             "read packet: $c#00",
-            {"direction": "send", "regex": r"[$]W00#.*"},
+            {"direction": "send", "regex": r"[$]W00;process:[0-9a-f]+#.*"},
         ], True)
         self.expect_gdbremote_sequence()
 
@@ -88,7 +88,7 @@
             "read packet: $c#00",
             {"direction": "send", "regex": r"[$]T.*vforkdone.*"},
             "read packet: $c#00",
-            {"direction": "send", "regex": r"[$]W00#.*"},
+            {"direction": "send", "regex": r"[$]W00;process:[0-9a-f]+#.*"},
         ], True)
         self.expect_gdbremote_sequence()
 
@@ -136,7 +136,7 @@
         # resume the child
         self.test_sequence.add_log_lines([
             "read packet: $c#00",
-            {"direction": "send", "regex": r"[$]W00#.*"},
+            {"direction": "send", "regex": r"[$]W00;process:[0-9a-f]+#.*"},
         ], True)
         self.expect_gdbremote_sequence()