diff --git a/include/oox/export/drawingml.hxx b/include/oox/export/drawingml.hxx
index 852387deec0b..2b3eb9eec8e7 100644
--- a/include/oox/export/drawingml.hxx
+++ b/include/oox/export/drawingml.hxx
@@ -123,8 +123,8 @@ public:
     OUString WriteImage( const Graphic &rGraphic , bool bRelPathToMedia = false);
 
     void WriteColor( sal_uInt32 nColor, sal_Int32 nAlpha = MAX_PERCENT );
-    void WriteColor( const OUString& sColorSchemeName, ::com::sun::star::uno::Sequence< ::com::sun::star::beans::PropertyValue > aTransformations );
-    void WriteColorTransformations( ::com::sun::star::uno::Sequence< ::com::sun::star::beans::PropertyValue > aTransformations );
+    void WriteColor( const OUString& sColorSchemeName, const ::com::sun::star::uno::Sequence< ::com::sun::star::beans::PropertyValue >& aTransformations );
+    void WriteColorTransformations( const ::com::sun::star::uno::Sequence< ::com::sun::star::beans::PropertyValue >& aTransformations );
     void WriteGradientStop( sal_uInt16 nStop, sal_uInt32 nColor );
     void WriteLineArrow( ::com::sun::star::uno::Reference< ::com::sun::star::beans::XPropertySet > rXPropSet, bool bLineStart );
     void WriteConnectorConnections( EscherConnectorListEntry& rConnectorEntry, sal_Int32 nStartID, sal_Int32 nEndID );
diff --git a/oox/source/export/drawingml.cxx b/oox/source/export/drawingml.cxx
index 99deb828904d..eff1d2bc6efd 100644
--- a/oox/source/export/drawingml.cxx
+++ b/oox/source/export/drawingml.cxx
@@ -181,7 +181,7 @@ void DrawingML::WriteColor( sal_uInt32 nColor, sal_Int32 nAlpha )
     }
 }
 
-void DrawingML::WriteColor( const OUString& sColorSchemeName, Sequence< PropertyValue > aTransformations )
+void DrawingML::WriteColor( const OUString& sColorSchemeName, const Sequence< PropertyValue >& aTransformations )
 {
     // prevent writing a tag with empty val attribute
     if( sColorSchemeName.isEmpty() )
@@ -201,7 +201,7 @@ void DrawingML::WriteColor( const OUString& sColorSchemeName, Sequence< Property
                               FSEND );
 }
 
-void DrawingML::WriteColorTransformations( Sequence< PropertyValue > aTransformations )
+void DrawingML::WriteColorTransformations( const Sequence< PropertyValue >& aTransformations )
 {
     for( sal_Int32 i = 0; i < aTransformations.getLength(); i++ )
     {