diff --git a/intern/cycles/blender/geometry.cpp b/intern/cycles/blender/geometry.cpp
index a576f8b1813..49b94ed8fe9 100644
--- a/intern/cycles/blender/geometry.cpp
+++ b/intern/cycles/blender/geometry.cpp
@@ -128,11 +128,6 @@ Geometry *BlenderSync::sync_geometry(BObjectInfo &b_ob_info,
   }
 
   if (!sync) {
-    /* Need to determine this every sync. */
-    if (geom->is_light() && static_cast<const Light *>(geom)->get_is_portal()) {
-      world_use_portal = true;
-    }
-
     /* If transform was applied to geometry, need full update. */
     if (object_updated && geom->transform_applied) {
       ;
diff --git a/intern/cycles/blender/light.cpp b/intern/cycles/blender/light.cpp
index ead162e9f91..9acb3aeb99e 100644
--- a/intern/cycles/blender/light.cpp
+++ b/intern/cycles/blender/light.cpp
@@ -108,10 +108,6 @@ void BlenderSync::sync_light(BObjectInfo &b_ob_info, Light *light)
     light->set_is_portal(false);
   }
 
-  if (light->get_is_portal()) {
-    world_use_portal = true;
-  }
-
   /* tag */
   light->tag_update(scene);
 }
@@ -173,9 +169,6 @@ void BlenderSync::sync_background_light(BL::SpaceView3D &b_v3d)
       light->set_use_mis(sample_as_light);
       light->set_max_bounces(get_int(cworld, "max_bounces"));
 
-      /* Force enable light again when world is resynced. */
-      light->set_is_enabled(sample_as_light || world_use_portal);
-
       /* Caustic light. */
       light->set_use_caustics(get_boolean(cworld, "is_caustics_light"));
 
diff --git a/intern/cycles/blender/object.cpp b/intern/cycles/blender/object.cpp
index 033a6c0a93d..edad26b428c 100644
--- a/intern/cycles/blender/object.cpp
+++ b/intern/cycles/blender/object.cpp
@@ -538,8 +538,6 @@ void BlenderSync::sync_objects(BL::Depsgraph &b_depsgraph,
     geometry_motion_synced.clear();
   }
 
-  world_use_portal = false;
-
   if (!motion) {
     /* Object to geometry instance mapping is built for the reference time, as other
      * times just look up the corresponding geometry. */
diff --git a/intern/cycles/blender/sync.h b/intern/cycles/blender/sync.h
index a9e18c8304b..75b99f6b615 100644
--- a/intern/cycles/blender/sync.h
+++ b/intern/cycles/blender/sync.h
@@ -237,7 +237,6 @@ class BlenderSync {
   set<float> motion_times;
   void *world_map;
   bool world_recalc;
-  bool world_use_portal = false;
   BlenderViewportParameters viewport_parameters;
 
   Scene *scene;
diff --git a/intern/cycles/scene/light.cpp b/intern/cycles/scene/light.cpp
index 07499e009ee..7095ef5d5e7 100644
--- a/intern/cycles/scene/light.cpp
+++ b/intern/cycles/scene/light.cpp
@@ -157,7 +157,8 @@ bool Light::has_contribution(const Scene *scene, const Object *object)
     return false;
   }
   if (light_type == LIGHT_BACKGROUND) {
-    return is_enabled;
+    /* Will be determined after finishing processing all the lights. */
+    return true;
   }
   if (light_type == LIGHT_AREA) {
     if ((get_sizeu() * get_sizev() * get_size() == 0.0f) ||
@@ -266,15 +267,12 @@ void LightManager::test_enabled_lights(Scene *scene)
     Light *light = static_cast<Light *>(object->get_geometry());
     light->is_enabled = light->has_contribution(scene, object);
     has_portal |= light->is_portal;
-    if (!light->is_enabled) {
-      continue;
-    }
 
     if (light->light_type == LIGHT_BACKGROUND) {
       background_lights.push_back(light);
     }
 
-    num_lights++;
+    num_lights += light->is_enabled;
   }
 
   LOG_INFO << "Total " << num_lights << " lights.";
@@ -288,14 +286,16 @@ void LightManager::test_enabled_lights(Scene *scene)
      * - If we don't need it (no HDRs etc.)
      */
     Shader *shader = scene->background->get_shader(scene);
-    const bool disable_mis = !(has_portal || shader->has_surface_spatial_varying);
-    if (disable_mis) {
-      LOG_INFO << "Background MIS has been disabled.";
-    }
     for (Light *light : background_lights) {
-      light->is_enabled = !disable_mis;
-      background_enabled = !disable_mis;
-      background_resolution = light->map_resolution;
+      light->is_enabled = has_portal || (light->use_mis && shader->has_surface_spatial_varying);
+      if (light->is_enabled) {
+        background_enabled = true;
+        background_resolution = light->map_resolution;
+      }
+    }
+
+    if (!background_enabled) {
+      LOG_INFO << "Background MIS has been disabled.";
     }
   }