diff --git a/src/Gui/ExpressionCompleter.cpp b/src/Gui/ExpressionCompleter.cpp
index 971b32e15c..2a69ac829c 100644
--- a/src/Gui/ExpressionCompleter.cpp
+++ b/src/Gui/ExpressionCompleter.cpp
@@ -388,6 +388,8 @@ QStringList ExpressionCompleter::splitPath ( const QString & input ) const
 
 void ExpressionCompleter::slotUpdate(const QString & prefix)
 {
+    init();
+
     using namespace boost::tuples;
     std::string completionPrefix;