diff --git a/src/app/qgsdiagramproperties.cpp b/src/app/qgsdiagramproperties.cpp
index f0cc449d80a..298bad2c924 100644
--- a/src/app/qgsdiagramproperties.cpp
+++ b/src/app/qgsdiagramproperties.cpp
@@ -343,6 +343,23 @@ void QgsDiagramProperties::on_mDiagramTypeComboBox_currentIndexChanged( int inde
     mScaleDependencyLabel->hide();
   }
 }
+void QgsDiagramProperties::addAttribute( QTreeWidgetItem * item )
+{
+  QTreeWidgetItem *newItem = new QTreeWidgetItem( mDiagramAttributesTreeWidget );
+
+  newItem->setText( 0, item->text( 0 ) );
+  newItem->setData( 0, Qt::UserRole, item->data( 0, Qt::UserRole ) );
+  newItem->setFlags( newItem->flags() & ~Qt::ItemIsDropEnabled );
+
+  //set initial color for diagram category
+  int red = 1 + ( int )( 255.0 * rand() / ( RAND_MAX + 1.0 ) );
+  int green = 1 + ( int )( 255.0 * rand() / ( RAND_MAX + 1.0 ) );
+  int blue = 1 + ( int )( 255.0 * rand() / ( RAND_MAX + 1.0 ) );
+  QColor randomColor( red, green, blue );
+  newItem->setBackground( 1, QBrush( randomColor ) );
+  mDiagramAttributesTreeWidget->addTopLevelItem( newItem );
+}
+
 
 void QgsDiagramProperties::on_mTransparencySlider_valueChanged( int value )
 {
@@ -353,22 +370,14 @@ void QgsDiagramProperties::on_mAddCategoryPushButton_clicked()
 {
   foreach ( QTreeWidgetItem *attributeItem, mAttributesTreeWidget->selectedItems() )
   {
-    QTreeWidgetItem *newItem = new QTreeWidgetItem( mDiagramAttributesTreeWidget );
-
-    newItem->setText( 0, attributeItem->text( 0 ) );
-    newItem->setData( 0, Qt::UserRole, attributeItem->data( 0, Qt::UserRole ) );
-    newItem->setFlags( newItem->flags() & ~Qt::ItemIsDropEnabled );
-
-    //set initial color for diagram category
-    int red = 1 + ( int )( 255.0 * rand() / ( RAND_MAX + 1.0 ) );
-    int green = 1 + ( int )( 255.0 * rand() / ( RAND_MAX + 1.0 ) );
-    int blue = 1 + ( int )( 255.0 * rand() / ( RAND_MAX + 1.0 ) );
-    QColor randomColor( red, green, blue );
-    newItem->setBackground( 1, QBrush( randomColor ) );
-    mDiagramAttributesTreeWidget->addTopLevelItem( newItem );
+    addAttribute( attributeItem );
   }
 }
 
+void QgsDiagramProperties::on_mAttributesTreeWidget_itemDoubleClicked( QTreeWidgetItem * item, int column )
+{
+  addAttribute( item );
+}
 
 void QgsDiagramProperties::on_mRemoveCategoryPushButton_clicked()
 {
diff --git a/src/app/qgsdiagramproperties.h b/src/app/qgsdiagramproperties.h
index 573e94b2952..88f15f5b34d 100644
--- a/src/app/qgsdiagramproperties.h
+++ b/src/app/qgsdiagramproperties.h
@@ -29,14 +29,15 @@ class QgsDiagramProperties : public QWidget, private Ui::QgsDiagramPropertiesBas
 
   public:
     QgsDiagramProperties( QgsVectorLayer* layer, QWidget* parent );
-
-    //void handleAttributeDoubleClicked( QTreeWidgetItem * item, int column );
+    /**Adds an attribute from the list of available attributes to the assigned attributes with a random color.*/
+    void addAttribute( QTreeWidgetItem * item );
 
   public slots:
     void apply();
     void on_mDiagramTypeComboBox_currentIndexChanged( int index );
     void on_mTransparencySlider_valueChanged( int value );
     void on_mAddCategoryPushButton_clicked();
+    void on_mAttributesTreeWidget_itemDoubleClicked( QTreeWidgetItem * item, int column );
     void on_mBackgroundColorButton_clicked();
     void on_mFindMaximumValueButton_clicked();
     void on_mDiagramPenColorButton_clicked();