diff --git a/Changes b/Changes
index ad79eb99c9..eb59755b6c 100644
--- a/Changes
+++ b/Changes
@@ -1,7 +1,10 @@
 10.7.x.x (relative to 10.7.0.0a12)
 ========
 
+Fixes
+-----
 
+- PointInstancer : Fixed signature for `setPrototypes()` function.
 
 10.7.0.0a12 (relative to 10.7.0.0a11)
 ===========
diff --git a/include/IECoreScene/PointInstancer.h b/include/IECoreScene/PointInstancer.h
index c12f0ada2c..a9975ab091 100644
--- a/include/IECoreScene/PointInstancer.h
+++ b/include/IECoreScene/PointInstancer.h
@@ -83,7 +83,7 @@ class IECORESCENE_API PointInstancer : public IECoreScene::PointsPrimitive
 		/// Sets the prototypes to be instanced. Interpretation is left to
 		/// the consuming rendering system, but in practice these are locations
 		/// in a SceneInterface or Gaffer scene.
-		void setPrototypes( IECore::StringVectorDataPtr &prototypes );
+		void setPrototypes( const IECore::StringVectorDataPtr &prototypes );
 		/// Returns an invalid view if the variable doesn't exist, or if it
 		/// exists but has the wrong type or interpolation.
 		PrimitiveVariable::IndexedView<std::string> getPrototypes() const;
diff --git a/src/IECoreScene/PointInstancer.cpp b/src/IECoreScene/PointInstancer.cpp
index 0e2be2ee37..245c1fd5d3 100644
--- a/src/IECoreScene/PointInstancer.cpp
+++ b/src/IECoreScene/PointInstancer.cpp
@@ -83,7 +83,7 @@ void PointInstancer::hash( MurmurHash &h ) const
 	PointsPrimitive::hash( h );
 }
 
-void PointInstancer::setPrototypes( IECore::StringVectorDataPtr &prototypes )
+void PointInstancer::setPrototypes( const IECore::StringVectorDataPtr &prototypes )
 {
 	if( prototypes )
 	{