diff --git a/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationClient.cpp b/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationClient.cpp
--- a/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationClient.cpp
+++ b/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationClient.cpp
@@ -2639,16 +2639,13 @@
   packet.PutChar('H');
   packet.PutChar(op);
 
-  if (pid != LLDB_INVALID_PROCESS_ID) {
-    packet.PutChar('p');
-    packet.PutHex64(pid);
-    packet.PutChar('.');
-  }
+  if (pid != LLDB_INVALID_PROCESS_ID)
+    packet.Printf("p%" PRIx64 ".", pid);
 
   if (tid == UINT64_MAX)
     packet.PutCString("-1");
   else
-    packet.PutHex64(tid);
+    packet.Printf("%" PRIx64, tid);
 
   StringExtractorGDBRemote response;
   if (SendPacketAndWaitForResponse(packet.GetString(), response) 
diff --git a/lldb/unittests/Process/gdb-remote/GDBRemoteCommunicationClientTest.cpp b/lldb/unittests/Process/gdb-remote/GDBRemoteCommunicationClientTest.cpp
--- a/lldb/unittests/Process/gdb-remote/GDBRemoteCommunicationClientTest.cpp
+++ b/lldb/unittests/Process/gdb-remote/GDBRemoteCommunicationClientTest.cpp
@@ -98,7 +98,7 @@
   });
 
   Handle_QThreadSuffixSupported(server, false);
-  HandlePacket(server, "Hg0000000000000047", "OK");
+  HandlePacket(server, "Hg47", "OK");
   HandlePacket(server, "P4=" + one_register_hex, "OK");
   ASSERT_TRUE(write_result.get());
 
@@ -143,7 +143,7 @@
     return client.SaveRegisterState(tid, save_id);
   });
   Handle_QThreadSuffixSupported(server, false);
-  HandlePacket(server, "Hg0000000000000047", "OK");
+  HandlePacket(server, "Hg47", "OK");
   HandlePacket(server, "QSaveRegisterState", "1");
   ASSERT_TRUE(async_result.get());
   EXPECT_EQ(1u, save_id);