diff --git a/sysbench/scripting/script_lua.c b/sysbench/scripting/script_lua.c
index 410eda8..7955af5 100644
--- a/sysbench/scripting/script_lua.c
+++ b/sysbench/scripting/script_lua.c
@@ -241,15 +241,18 @@ sb_request_t sb_lua_get_request(int thread_id)
 
   (void) thread_id; /* unused */
 
+  SB_THREAD_MUTEX_LOCK();
   if (sb_globals.max_requests != 0 && nevents >= sb_globals.max_requests)
   {
     req.type = SB_REQ_TYPE_NULL;
+    SB_THREAD_MUTEX_UNLOCK();
     return req;
   }
 
   req.type = SB_REQ_TYPE_SCRIPT;
   nevents++;
-  
+  SB_THREAD_MUTEX_UNLOCK();
+ 
   return req;
 }