diff --git a/intern/cycles/blender/addon/properties.py b/intern/cycles/blender/addon/properties.py
index 3007c44a20c..c23f0196c2d 100644
--- a/intern/cycles/blender/addon/properties.py
+++ b/intern/cycles/blender/addon/properties.py
@@ -235,6 +235,13 @@ class CyclesRenderSettings(bpy.types.PropertyGroup):
                 default=0.0,
                 )
 
+        cls.debug_tile_size = IntProperty(
+                name="Tile Size",
+                description="",
+                min=1, max=4096,
+                default=1024,
+                )
+
         cls.resolution_divider = IntProperty(
                 name="Resolution Divider",
                 description="Start viewport rendering with lower resolution which would be real resolution divided by two in power of this value",
diff --git a/intern/cycles/blender/blender_sync.cpp b/intern/cycles/blender/blender_sync.cpp
index c44a3902f73..d35c93ccbd2 100644
--- a/intern/cycles/blender/blender_sync.cpp
+++ b/intern/cycles/blender/blender_sync.cpp
@@ -344,10 +344,24 @@ SessionParams BlenderSync::get_session_params(BL::RenderEngine b_engine, BL::Use
 	}
 
 	/* tiles */
-	int tile_x = b_engine.tile_x();
-	int tile_y = b_engine.tile_y();
+	if(params.device.type != DEVICE_CPU && !background) {
+		printf("%d\n", get_int(cscene, "debug_tile_size"));
+
+		/* currently GPU could be much slower than CPU when using tiles,
+		 * still need to be investigated, but meanwhile make it possible
+		 * to work in viewport smoothly
+		 */
+		int debug_tile_size = get_int(cscene, "debug_tile_size");
+
+		params.tile_size = make_int2(debug_tile_size, debug_tile_size);
+	}
+	else {
+		int tile_x = b_engine.tile_x();
+		int tile_y = b_engine.tile_y();
+
+		params.tile_size = make_int2(tile_x, tile_y);
+	}
 
-	params.tile_size = make_int2(tile_x, tile_y);
 	params.resolution = 1 << get_int(cscene, "resolution_divider");
 
 	/* other parameters */