diff --git a/intern/cycles/blender/addon/ui.py b/intern/cycles/blender/addon/ui.py
index 10754ed6b9f..94a48e6c42d 100644
--- a/intern/cycles/blender/addon/ui.py
+++ b/intern/cycles/blender/addon/ui.py
@@ -431,6 +431,7 @@ class CyclesWorld_PT_surface(CyclesButtonsPanel, Panel):
 class CyclesWorld_PT_volume(CyclesButtonsPanel, Panel):
     bl_label = "Volume"
     bl_context = "world"
+    bl_options = {'DEFAULT_CLOSED'}
 
     @classmethod
     def poll(cls, context):
@@ -460,6 +461,7 @@ class CyclesMaterial_PT_surface(CyclesButtonsPanel, Panel):
 class CyclesMaterial_PT_volume(CyclesButtonsPanel, Panel):
     bl_label = "Volume"
     bl_context = "material"
+    bl_options = {'DEFAULT_CLOSED'}
 
     @classmethod
     def poll(cls, context):
diff --git a/intern/cycles/kernel/svm/svm.h b/intern/cycles/kernel/svm/svm.h
index 62e02f1a01a..9628f96bcab 100644
--- a/intern/cycles/kernel/svm/svm.h
+++ b/intern/cycles/kernel/svm/svm.h
@@ -179,7 +179,7 @@ __device_noinline void svm_eval_nodes(KernelGlobals *kg, ShaderData *sd, ShaderT
 				svm_node_closure_emission(sd, stack, node);
 				break;
 			case NODE_CLOSURE_BACKGROUND:
-				svm_node_closure_background(sd, node);
+				svm_node_closure_background(sd, stack, node);
 				break;
 			case NODE_CLOSURE_HOLDOUT:
 				svm_node_closure_holdout(sd, stack, node);
diff --git a/intern/cycles/kernel/svm/svm_closure.h b/intern/cycles/kernel/svm/svm_closure.h
index 90636380e43..fcda7ac6fe1 100644
--- a/intern/cycles/kernel/svm/svm_closure.h
+++ b/intern/cycles/kernel/svm/svm_closure.h
@@ -236,7 +236,6 @@ __device void svm_node_closure_volume(KernelGlobals *kg, ShaderData *sd, float *
 __device void svm_node_closure_emission(ShaderData *sd, float *stack, uint4 node)
 {
 #ifdef __MULTI_CLOSURE__
-	ShaderClosure *sc = svm_node_closure_get(sd);
 	uint mix_weight_offset = node.y;
 
 	if(stack_valid(mix_weight_offset)) {
@@ -245,31 +244,52 @@ __device void svm_node_closure_emission(ShaderData *sd, float *stack, uint4 node
 		if(mix_weight == 0.0f)
 			return;
 
+		ShaderClosure *sc = svm_node_closure_get(sd);
 		sc->weight *= mix_weight;
+		sc->type = CLOSURE_EMISSION_ID;
 	}
+	else {
+		ShaderClosure *sc = svm_node_closure_get(sd);
+		sc->type = CLOSURE_EMISSION_ID;
+	}
+
 #else
 	ShaderClosure *sc = &sd->closure;
+	sc->type = CLOSURE_EMISSION_ID;
 #endif
 
-	sc->type = CLOSURE_EMISSION_ID;
 	sd->flag |= SD_EMISSION;
 }
 
-__device void svm_node_closure_background(ShaderData *sd, uint4 node)
+__device void svm_node_closure_background(ShaderData *sd, float *stack, uint4 node)
 {
 #ifdef __MULTI_CLOSURE__
-	ShaderClosure *sc = svm_node_closure_get(sd);
+	uint mix_weight_offset = node.y;
+
+	if(stack_valid(mix_weight_offset)) {
+		float mix_weight = stack_load_float(stack, mix_weight_offset);
+
+		if(mix_weight == 0.0f)
+			return;
+
+		ShaderClosure *sc = svm_node_closure_get(sd);
+		sc->weight *= mix_weight;
+		sc->type = CLOSURE_BACKGROUND_ID;
+	}
+	else {
+		ShaderClosure *sc = svm_node_closure_get(sd);
+		sc->type = CLOSURE_BACKGROUND_ID;
+	}
+
 #else
 	ShaderClosure *sc = &sd->closure;
-#endif
-
 	sc->type = CLOSURE_BACKGROUND_ID;
+#endif
 }
 
 __device void svm_node_closure_holdout(ShaderData *sd, float *stack, uint4 node)
 {
 #ifdef __MULTI_CLOSURE__
-	ShaderClosure *sc = svm_node_closure_get(sd);
 	uint mix_weight_offset = node.y;
 
 	if(stack_valid(mix_weight_offset)) {
@@ -278,17 +298,20 @@ __device void svm_node_closure_holdout(ShaderData *sd, float *stack, uint4 node)
 		if(mix_weight == 0.0f)
 			return;
 
+		ShaderClosure *sc = svm_node_closure_get(sd);
 		sc->weight = make_float3(mix_weight, mix_weight, mix_weight);
+		sc->type = CLOSURE_HOLDOUT_ID;
 	}
-	else
+	else {
+		ShaderClosure *sc = svm_node_closure_get(sd);
 		sc->weight = make_float3(1.0f, 1.0f, 1.0f);
-
-	sc->sample_weight = 0.0f;
+		sc->type = CLOSURE_HOLDOUT_ID;
+	}
 #else
 	ShaderClosure *sc = &sd->closure;
+	sc->type = CLOSURE_HOLDOUT_ID;
 #endif
 
-	sc->type = CLOSURE_HOLDOUT_ID;
 	sd->flag |= SD_HOLDOUT;
 }
 
diff --git a/intern/cycles/render/nodes.cpp b/intern/cycles/render/nodes.cpp
index e6aff8590ad..9c72c01417a 100644
--- a/intern/cycles/render/nodes.cpp
+++ b/intern/cycles/render/nodes.cpp
@@ -1370,7 +1370,7 @@ void BackgroundNode::compile(SVMCompiler& compiler)
 	else
 		compiler.add_node(NODE_CLOSURE_SET_WEIGHT, color_in->value*strength_in->value.x);
 
-	compiler.add_node(NODE_CLOSURE_BACKGROUND, CLOSURE_BACKGROUND_ID);
+	compiler.add_node(NODE_CLOSURE_BACKGROUND, compiler.closure_mix_weight_offset());
 }
 
 void BackgroundNode::compile(OSLCompiler& compiler)