diff --git a/lldb/source/Core/Debugger.cpp b/lldb/source/Core/Debugger.cpp
--- a/lldb/source/Core/Debugger.cpp
+++ b/lldb/source/Core/Debugger.cpp
@@ -1616,7 +1616,7 @@
 
 lldb::thread_result_t Debugger::EventHandlerThread(lldb::thread_arg_t arg) {
   ((Debugger *)arg)->DefaultEventHandler();
-  return nullptr;
+  return NULL;
 }
 
 bool Debugger::StartEventHandlerThread() {