diff --git a/src/plugins/cpptools/cppcompletionassist.cpp b/src/plugins/cpptools/cppcompletionassist.cpp
index a2cdde1ca72..0b1eff5066c 100644
--- a/src/plugins/cpptools/cppcompletionassist.cpp
+++ b/src/plugins/cpptools/cppcompletionassist.cpp
@@ -1205,7 +1205,7 @@ bool CppCompletionAssistProcessor::objcKeywordsWanted() const
             || mt == QLatin1String(CppTools::Constants::OBJECTIVE_CPP_SOURCE_MIMETYPE);
 }
 
-int CppCompletionAssistProcessor::startCompletionInternal(const QString fileName,
+int CppCompletionAssistProcessor::startCompletionInternal(const QString &fileName,
                                                           unsigned line, unsigned column,
                                                           const QString &expr,
                                                           int endOfExpression)
diff --git a/src/plugins/cpptools/cppcompletionassist.h b/src/plugins/cpptools/cppcompletionassist.h
index 4c952afb90a..89a5c4c16ec 100644
--- a/src/plugins/cpptools/cppcompletionassist.h
+++ b/src/plugins/cpptools/cppcompletionassist.h
@@ -121,7 +121,7 @@ private:
     int startCompletionHelper();
     bool tryObjCCompletion();
     bool objcKeywordsWanted() const;
-    int startCompletionInternal(const QString fileName,
+    int startCompletionInternal(const QString &fileName,
                                 unsigned line, unsigned column,
                                 const QString &expression,
                                 int endOfExpression);