diff --git a/arangod/Aql/RestAqlHandler.cpp b/arangod/Aql/RestAqlHandler.cpp
index 882ecb47de..01fd8d4c4b 100644
--- a/arangod/Aql/RestAqlHandler.cpp
+++ b/arangod/Aql/RestAqlHandler.cpp
@@ -32,6 +32,7 @@
 #include "Aql/ExecutionBlock.h"
 #include "Basics/ConditionLocker.h"
 #include "Basics/StringUtils.h"
+#include "Dispatcher/DispatcherThread.h"
 #include "HttpServer/HttpServer.h"
 #include "HttpServer/HttpHandlerFactory.h"
 #include "Rest/HttpRequest.h"
@@ -694,16 +695,28 @@ void RestAqlHandler::handleUseQuery (std::string const& operation,
   Json answerBody(Json::Object, 3);
 
   if (operation == "lock") {
+    // Mark current thread as potentially blocking:
+    auto currentThread = triagens::rest::DispatcherThread::currentDispatcherThread;
+
+    if (currentThread != nullptr) {
+      triagens::rest::DispatcherThread::currentDispatcherThread->blockThread();
+    }
     int res = TRI_ERROR_INTERNAL;
     try {
       res = query->trx()->lockCollections();
     }
     catch (...) {
       LOG_ERROR("lock lead to an exception");
+      if (currentThread != nullptr) {
+        triagens::rest::DispatcherThread::currentDispatcherThread->unblockThread();
+      }
       generateError(HttpResponse::SERVER_ERROR, TRI_ERROR_HTTP_SERVER_ERROR,
                     "lock lead to an exception");
       return;
     }
+    if (currentThread != nullptr) {
+      triagens::rest::DispatcherThread::currentDispatcherThread->unblockThread();
+    }
     answerBody("error", res == TRI_ERROR_NO_ERROR ? Json(false) : Json(true))
               ("code", Json(static_cast<double>(res)));
   }
diff --git a/arangod/V8Server/ApplicationV8.cpp b/arangod/V8Server/ApplicationV8.cpp
index 3d5a91837c..14232e68ed 100644
--- a/arangod/V8Server/ApplicationV8.cpp
+++ b/arangod/V8Server/ApplicationV8.cpp
@@ -47,6 +47,7 @@
 #include "Basics/tri-strings.h"
 #include "Cluster/ServerState.h"
 #include "Cluster/v8-cluster.h"
+#include "Dispatcher/DispatcherThread.h"
 #include "Dispatcher/ApplicationDispatcher.h"
 #include "Rest/HttpRequest.h"
 #include "Scheduler/ApplicationScheduler.h"
@@ -358,7 +359,15 @@ ApplicationV8::V8Context* ApplicationV8::enterContext (std::string const& name,
 
   while (_freeContexts[name].empty() && ! _stopping) {
     LOG_DEBUG("waiting for unused V8 context");
+    auto currentThread = triagens::rest::DispatcherThread::currentDispatcherThread;
+
+    if (currentThread != nullptr) {
+      triagens::rest::DispatcherThread::currentDispatcherThread->blockThread();
+    }
     guard.wait();
+    if (currentThread != nullptr) {
+      triagens::rest::DispatcherThread::currentDispatcherThread->unblockThread();
+    }
   }
 
   // in case we are in the shutdown phase, do not enter a context!