diff --git a/src/plugins/cpptools/cpplocatordata.cpp b/src/plugins/cpptools/cpplocatordata.cpp
index be2b948a96b..3154f66ddba 100644
--- a/src/plugins/cpptools/cpplocatordata.cpp
+++ b/src/plugins/cpptools/cpplocatordata.cpp
@@ -86,7 +86,6 @@ void CppLocatorData::onAboutToRemoveFiles(const QStringList &files)
 void CppLocatorData::flushPendingDocument(bool force) const
 {
     // TODO: move this off the UI thread and into a future.
-    QMutexLocker locker(&m_pendingDocumentsMutex);
     if (!force && m_pendingDocuments.size() < MaxPendingDocuments)
         return;
     if (m_pendingDocuments.isEmpty())
@@ -98,12 +97,3 @@ void CppLocatorData::flushPendingDocument(bool force) const
     m_pendingDocuments.clear();
     m_pendingDocuments.reserve(MaxPendingDocuments);
 }
-
-QList<IndexItem::Ptr> CppLocatorData::allIndexItems(
-        const QHash<QString, QList<IndexItem::Ptr>> &items) const
-{
-    QList<IndexItem::Ptr> result;
-    for (const QList<IndexItem::Ptr> &subItems : items)
-        result.append(subItems);
-    return result;
-}
diff --git a/src/plugins/cpptools/cpplocatordata.h b/src/plugins/cpptools/cpplocatordata.h
index b41bce07bfb..f8c853471f6 100644
--- a/src/plugins/cpptools/cpplocatordata.h
+++ b/src/plugins/cpptools/cpplocatordata.h
@@ -46,8 +46,8 @@ class CppLocatorData : public QObject
 public:
     void filterAllFiles(IndexItem::Visitor func) const
     {
-        flushPendingDocument(true);
         QMutexLocker locker(&m_pendingDocumentsMutex);
+        flushPendingDocument(true);
         QHash<QString, IndexItem::Ptr> infosByFile = m_infosByFile;
         locker.unlock();
         for (auto i = infosByFile.constBegin(), ei = infosByFile.constEnd(); i != ei; ++i)
@@ -60,13 +60,13 @@ public slots:
     void onAboutToRemoveFiles(const QStringList &files);
 
 private:
+    // Ensure to protect every call to this method with m_pendingDocumentsMutex
     void flushPendingDocument(bool force) const;
-    QList<IndexItem::Ptr> allIndexItems(const QHash<QString, QList<IndexItem::Ptr>> &items) const;
 
     mutable SearchSymbols m_search;
     mutable QHash<QString, IndexItem::Ptr> m_infosByFile;
 
-    mutable QRecursiveMutex m_pendingDocumentsMutex;
+    mutable QMutex m_pendingDocumentsMutex;
     mutable QVector<CPlusPlus::Document::Ptr> m_pendingDocuments;
 };