diff --git a/python/core/qgsfeaturesink.sip b/python/core/qgsfeaturesink.sip
index 0680c5695eb..11395d6504c 100644
--- a/python/core/qgsfeaturesink.sip
+++ b/python/core/qgsfeaturesink.sip
@@ -24,7 +24,7 @@ class QgsFeatureSink
 
     virtual ~QgsFeatureSink();
 
-    virtual bool addFeature( QgsFeature &feature ) = 0;
+    virtual bool addFeature( QgsFeature &feature /In,Out/ ) = 0;
 %Docstring
  Adds a single ``feature`` to the sink.
  \see addFeatures()
@@ -32,7 +32,7 @@ class QgsFeatureSink
  :rtype: bool
 %End
 
-    virtual bool addFeatures( QgsFeatureList &features ) = 0;
+    virtual bool addFeatures( QgsFeatureList &features /In,Out/ ) = 0;
 %Docstring
  Adds a list of ``features`` to the sink.
  \see addFeature()
diff --git a/src/core/qgsfeaturesink.h b/src/core/qgsfeaturesink.h
index 0bfd37835a9..8d2b7cb1ae0 100644
--- a/src/core/qgsfeaturesink.h
+++ b/src/core/qgsfeaturesink.h
@@ -40,14 +40,14 @@ class CORE_EXPORT QgsFeatureSink
      * \see addFeatures()
      * \returns true in case of success and false in case of failure
      */
-    virtual bool addFeature( QgsFeature &feature ) = 0;
+    virtual bool addFeature( QgsFeature &feature SIP_INOUT ) = 0;
 
     /**
      * Adds a list of \a features to the sink.
      * \see addFeature()
      * \returns true in case of success and false in case of failure
      */
-    virtual bool addFeatures( QgsFeatureList &features ) = 0;
+    virtual bool addFeatures( QgsFeatureList &features SIP_INOUT ) = 0;
 
 };