diff --git a/src/gui/Gui.cpp b/src/gui/Gui.cpp
index 49729ba27e8415e94dfdf2865c2cab9b2621bc07..3a4f374128ed58a53f096514c200a6df3075dad6 100644
--- a/src/gui/Gui.cpp
+++ b/src/gui/Gui.cpp
@@ -158,7 +158,7 @@ DisplayAdaptor * GUI::findDisplayAdaptorForBlockID ( ConstBlockDataID bdId ) con
 }
 
 
-void GUI::registerPropertyTree( const shared_ptr<PropertyTree> propertyTree ) {
+void GUI::registerPropertyTree( const shared_ptr<PropertyTree>& propertyTree ) {
    pImpl->propertyTrees_.push_back( propertyTree );
 }