diff --git a/lldb/tools/lldb-dap/Handler/RequestHandler.cpp b/lldb/tools/lldb-dap/Handler/RequestHandler.cpp
index 3520dc2c71a55..be9273963654a 100644
--- a/lldb/tools/lldb-dap/Handler/RequestHandler.cpp
+++ b/lldb/tools/lldb-dap/Handler/RequestHandler.cpp
@@ -14,6 +14,7 @@
 #include "Protocol/ProtocolBase.h"
 #include "RunInTerminal.h"
 #include "llvm/Support/Error.h"
+#include <mutex>
 
 #if !defined(_WIN32)
 #include <unistd.h>
@@ -180,6 +181,9 @@ void BaseRequestHandler::Run(const Request &request) {
     return;
   }
 
+  lldb::SBMutex lock = dap.GetAPIMutex();
+  std::lock_guard<lldb::SBMutex> guard(lock);
+
   // FIXME: After all the requests have migrated from LegacyRequestHandler >
   // RequestHandler<> we should be able to move this into
   // RequestHandler<>::operator().