diff --git a/src/mongo/db/repl/oplog.cpp b/src/mongo/db/repl/oplog.cpp
index a672dfeb78..546016d110 100644
--- a/src/mongo/db/repl/oplog.cpp
+++ b/src/mongo/db/repl/oplog.cpp
@@ -159,6 +159,13 @@ void _getNextOpTimes(OperationContext* opCtx,
         term = replCoord->getTerm();
     }
 
+#if 1
+    {
+	// XXX hack to move begin_transaction out of lock.
+	opCtx->recoveryUnit()->ensureSession();
+    }
+#endif
+
     stdx::lock_guard<stdx::mutex> lk(newOpMutex);
 
     auto ts = LogicalClock::get(opCtx)->reserveTicks(count).asTimestamp();
diff --git a/src/mongo/db/storage/recovery_unit.h b/src/mongo/db/storage/recovery_unit.h
index fe9ed47316..2e74199f91 100644
--- a/src/mongo/db/storage/recovery_unit.h
+++ b/src/mongo/db/storage/recovery_unit.h
@@ -71,6 +71,11 @@ public:
     virtual void abortUnitOfWork() = 0;
 
     /**
+     * Ensure that a session is allocated.
+     */
+    virtual void ensureSession() {};
+
+    /**
      * Waits until all commits that happened before this call are durable. Returns true, unless the
      * storage engine cannot guarantee durability, which should never happen when isDurable()
      * returned true. This cannot be called from inside a unit of work, and should fail if it is.
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_recovery_unit.h b/src/mongo/db/storage/wiredtiger/wiredtiger_recovery_unit.h
index 397d17a142..90c060b278 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_recovery_unit.h
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_recovery_unit.h
@@ -65,6 +65,8 @@ public:
     void commitUnitOfWork() override;
     void abortUnitOfWork() override;
 
+    void ensureSession() override { (void)getSession(); }
+
     bool waitUntilDurable() override;
 
     void registerChange(Change* change) override;