--- a/gfx/wr/webrender/src/picture.rs
+++ b/gfx/wr/webrender/src/picture.rs
@@ -2423,16 +2423,21 @@ impl TileCacheInstance {
                 if tile.is_visible {
                     world_culling_rect = world_culling_rect.union(&tile.world_tile_rect);
                 }
 
                 self.tiles.insert(key, tile);
             }
         }
 
+        // When old tiles that remain after the loop, dirty rects are not valid.
+        if !self.old_tiles.is_empty() {
+            frame_state.composite_state.dirty_rects_are_valid = false;
+        }
+
         // Any old tiles that remain after the loop above are going to be dropped. For
         // simple composite mode, the texture cache handle will expire and be collected
         // by the texture cache. For native compositor mode, we need to explicitly
         // invoke a callback to the client to destroy that surface.
         frame_state.composite_state.destroy_native_tiles(
             self.old_tiles.values_mut(),
             frame_state.resource_cache,
         );