diff --git a/src/Mod/Sketcher/Gui/PropertyConstraintListItem.cpp b/src/Mod/Sketcher/Gui/PropertyConstraintListItem.cpp
index 63bb8b7504..dd3c4ed318 100644
--- a/src/Mod/Sketcher/Gui/PropertyConstraintListItem.cpp
+++ b/src/Mod/Sketcher/Gui/PropertyConstraintListItem.cpp
@@ -23,6 +23,7 @@
 #include "PreCompiled.h"
 
 #ifndef _PreComp_
+# include <QDebug>
 # include <QTextStream>
 #endif
 
@@ -44,6 +45,10 @@ PropertyConstraintListItem::PropertyConstraintListItem()
     onlyUnnamed = false;
 }
 
+PropertyConstraintListItem::~PropertyConstraintListItem()
+{
+}
+
 QVariant PropertyConstraintListItem::toString(const QVariant& prop) const
 {
     const QList<Base::Quantity>& value = prop.value< QList<Base::Quantity> >();
@@ -175,10 +180,17 @@ QVariant PropertyConstraintListItem::value(const App::Property* prop) const
             if ((*it)->Name.empty() && !onlyUnnamed) {
                 onlyNamed = false;
                 subquantities.append(quant);
-                PropertyConstraintListItem* unnamednode = static_cast<PropertyConstraintListItem*>(self->child(self->childCount()-1));
-                unnamednode->blockEvent = true;
-                unnamednode->setProperty(internalName.toLatin1(), QVariant::fromValue<Base::Quantity>(quant));
-                unnamednode->blockEvent = false;
+                PropertyItem* child = self->child(self->childCount()-1);
+                PropertyConstraintListItem* unnamednode = qobject_cast<PropertyConstraintListItem*>(child);
+                if (unnamednode) {
+                    unnamednode->blockEvent = true;
+                    unnamednode->setProperty(internalName.toLatin1(), QVariant::fromValue<Base::Quantity>(quant));
+                    unnamednode->blockEvent = false;
+                }
+                else {
+                    qWarning() << "Item is not of type PropertyConstraintListItem but"
+                               << typeid(*child).name();
+                }
             }
             else {
                 self->setProperty(internalName.toLatin1(), QVariant::fromValue<Base::Quantity>(quant));
diff --git a/src/Mod/Sketcher/Gui/PropertyConstraintListItem.h b/src/Mod/Sketcher/Gui/PropertyConstraintListItem.h
index 381fb09566..e3ae30d4fd 100644
--- a/src/Mod/Sketcher/Gui/PropertyConstraintListItem.h
+++ b/src/Mod/Sketcher/Gui/PropertyConstraintListItem.h
@@ -45,6 +45,7 @@ class PropertyConstraintListItem: public Gui::PropertyEditor::PropertyItem
     Q_OBJECT
     PROPERTYITEM_HEADER
 
+    virtual ~PropertyConstraintListItem();
     virtual QWidget* createEditor(QWidget* parent, const QObject* receiver, const char* method) const;
     virtual void setEditorData(QWidget *editor, const QVariant& data) const;
     virtual QVariant editorData(QWidget *editor) const;