2 files changed, 2 insertions, 2 deletions
diff --git a/graph.cpp b/graph.cpp
index 7ad7e9931..a77f658e6 100644
--- a/graph.cpp
+++ b/graph.cpp
@@ -114,7 +114,7 @@ void Graph::dump() const
     }
 }
 
-void Graph::dumpDot(const QHash< int, QString > nodeNames, const QString& fileName) const
+void Graph::dumpDot(const QHash< int, QString >& nodeNames, const QString& fileName) const
 {
     QFile output(fileName);
     if (!output.open(QIODevice::WriteOnly))
diff --git a/graph.h b/graph.h
index 2cc0a8f43..d3a754e98 100644
--- a/graph.h
+++ b/graph.h
@@ -52,7 +52,7 @@ public:
     *   \param nodeNames map used to translate node ids to human readable text.
     *   \param fileName file name where the output should be written.
     */
-    void dumpDot(const QHash<int, QString> nodeNames, const QString& fileName) const;
+    void dumpDot(const QHash<int, QString>& nodeNames, const QString& fileName) const;
 
     /**
     *   Topologically sort this graph.