diff --git a/.github/workflows/main/installDependencies.py b/.github/workflows/main/installDependencies.py
index 69ec7d13983..ef04c7f7dad 100755
--- a/.github/workflows/main/installDependencies.py
+++ b/.github/workflows/main/installDependencies.py
@@ -48,7 +48,7 @@
 
 # Determine default archive URL.
 
-defaultURL = "https://github.com/GafferHQ/dependencies/releases/download/7.0.0/gafferDependencies-7.0.0-{platform}.{extension}".format(
+defaultURL = "https://github.com/ImageEngine/cortex/releases/download/10.5.1.0/cortex-10.5.1.0-{platform}-python3.{extension}".format(
 	platform = { "darwin" : "osx", "win32" : "windows" }.get( sys.platform, "linux" ),
 	extension = "tar.gz" if sys.platform != "win32" else "zip"
 )
diff --git a/Changes.md b/Changes.md
index d7d4795ead2..4dfef34bb67 100644
--- a/Changes.md
+++ b/Changes.md
@@ -1,4 +1,4 @@
-1.3.x.x (relative to 1.3.0.0)
+1.3.1.0 (relative to 1.3.0.0)
 =======
 
 Features
@@ -6,6 +6,7 @@ Features
 
 - USDShader : Added a node for loading shaders from USD's `SdrRegistry`. This includes shaders such as `UsdPreviewSurface` and `UsdUVTexture`, which are now available in the `USD/Shader` section of the node menu.
 - USDLight : Added a node for defining UsdLux lights. This is available from the `USD/Light` section of the node menu.
+- SceneReader, SceneWriter : Added limited support for reading and writing Usd Volume prims.
 
 Improvements
 ------------
@@ -13,11 +14,12 @@ Improvements
 - LightEditor : Added section displaying UsdLux shadow parameters.
 - Cycles : Added support for UsdLux lights.
 - LightTool : Added support for editing animated plugs.
-- Median/Erode/Dilate : Dramatic speedup of these nodes for wide filters. Measured improvements of 100X faster for Erode/Dilate, and 10X faster for Median.
+- Median, Erode, Dilate : Improved performance significantly for wide filters. Measured improvements of 100x faster for Erode/Dilate, and 10x faster for Median.
 
 Fixes
 -----
 
+- SceneWriter : Fixed writing of UsdLux lights.
 - Viewer : Fixed visualisation of shaping cones for UsdLux lights, which were previously drawn at half the correct angle.
 - DisplayTransform : Fixed missing `view` presets when `display` is at the default value (#5392).
 - Arnold
@@ -43,6 +45,11 @@ API
 - OptionalValuePlug : Added a new plug type that pairs an `enabled` BoolPlug with a `value` ValuePlug.
 - Shader : Added support for using OptionalValuePlug to represent optional parameters.
 
+Build
+-----
+
+- Cortex : Updated to version 10.5.1.0.
+
 1.3.0.0 (relative to 1.2.10.0)
 =======
 
diff --git a/SConstruct b/SConstruct
index c5ea59a0baa..9a40a95597b 100644
--- a/SConstruct
+++ b/SConstruct
@@ -62,7 +62,7 @@ if codecs.lookup( locale.getpreferredencoding() ).name != "utf-8" :
 
 gafferMilestoneVersion = 1 # for announcing major milestones - may contain all of the below
 gafferMajorVersion = 3 # backwards-incompatible changes
-gafferMinorVersion = 0 # new backwards-compatible features
+gafferMinorVersion = 1 # new backwards-compatible features
 gafferPatchVersion = 0 # bug fixes
 gafferVersionSuffix = "" # used for alpha/beta releases : "a1", "b2", etc.
 
diff --git a/python/GafferSceneTest/SceneReaderTest.py b/python/GafferSceneTest/SceneReaderTest.py
index 5c9bfd5e301..894cb6c0d0d 100644
--- a/python/GafferSceneTest/SceneReaderTest.py
+++ b/python/GafferSceneTest/SceneReaderTest.py
@@ -617,9 +617,13 @@ def testExplicitUSDDefaultLights( self ) :
 
 		light1 = GafferSceneTest.TestLight()
 		light1["name"].setValue( "light1" )
+		light1["lightShaderName"].setValue( "SphereLight" ) # USDScene requires valid USD light type
+		light1["parameters"]["intensity"] = Gaffer.FloatPlug( defaultValue = 1 ) # USD expects float, not colour
 		light1["defaultLight"].setValue( False )
 
 		light2 = GafferSceneTest.TestLight()
+		light2["lightShaderName"].setValue( "SphereLight" )
+		light2["parameters"]["intensity"] = Gaffer.FloatPlug( defaultValue = 1 )
 		light2["name"].setValue( "light2" )
 
 		group = GafferScene.Group()
diff --git a/src/GafferSceneTest/TestLight.cpp b/src/GafferSceneTest/TestLight.cpp
index 5bc2f29d7e6..cbdfe03648c 100644
--- a/src/GafferSceneTest/TestLight.cpp
+++ b/src/GafferSceneTest/TestLight.cpp
@@ -49,6 +49,7 @@ GAFFER_NODE_DEFINE_TYPE( TestLight )
 TestLight::TestLight( const std::string &name )
 	:	Light( name )
 {
+	addChild( new StringPlug( "lightShaderName", Plug::In, "testLight" ) );
 	parametersPlug()->addChild( new Color3fPlug( "intensity" ) );
 	parametersPlug()->addChild( new FloatPlug( "exposure" ) );
 	parametersPlug()->addChild( new BoolPlug( "__areaLight" ) );
@@ -68,7 +69,7 @@ void TestLight::hashLight( const Gaffer::Context *context, IECore::MurmurHash &h
 
 IECoreScene::ConstShaderNetworkPtr TestLight::computeLight( const Gaffer::Context *context ) const
 {
-	IECoreScene::ShaderPtr shader = new IECoreScene::Shader( "testLight", "light" );
+	IECoreScene::ShaderPtr shader = new IECoreScene::Shader( getChild<StringPlug>( "lightShaderName" )->getValue(), "light" );
 
 	for( const auto &c : ValuePlug::Range( *parametersPlug() ) )
 	{