diff --git a/away3d/materials/compilation/ShaderCompiler.hx b/away3d/materials/compilation/ShaderCompiler.hx
index 90578e21..35238173 100644
--- a/away3d/materials/compilation/ShaderCompiler.hx
+++ b/away3d/materials/compilation/ShaderCompiler.hx
@@ -310,6 +310,15 @@ class ShaderCompiler
 		_vertexCode = "";
 		_fragmentCode = "";
 
+		if (_sharedRegisters.custom != null)
+		{
+			#if haxe4
+			_sharedRegisters.custom.clear();
+			#else
+			_sharedRegisters.custom = null;
+			#end
+		}
+
 		_sharedRegisters.localPosition = _registerCache.getFreeVertexVectorTemp();
 		_registerCache.addVertexTempUsages(_sharedRegisters.localPosition, 1);
 
diff --git a/away3d/materials/compilation/ShaderRegisterData.hx b/away3d/materials/compilation/ShaderRegisterData.hx
index c7c6808e..21b35c74 100644
--- a/away3d/materials/compilation/ShaderRegisterData.hx
+++ b/away3d/materials/compilation/ShaderRegisterData.hx
@@ -25,6 +25,12 @@ class ShaderRegisterData
 	public var viewDirFragment:ShaderRegisterElement;
 	public var bitangent:ShaderRegisterElement;
 	
+	/**
+	 * Space for named registers other than the ones above. Will be null until
+	 * defined by an effect method.
+	 */
+	public var custom:Map<String, ShaderRegisterElement> = null;
+	
 	public function new()
 	{