diff --git a/CHANGELOG.md b/CHANGELOG.md
index 316163c8..11e78952 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,10 @@ All notable changes to [bpmn-js](https://github.com/bpmn-io/bpmn-js) are documen
 
 ___Note:__ Yet to be released changes appear here._
 
+## 1.2.1
+
+* `FIX`: correct side-effects config to not include `*.css` files
+
 ## 1.2.0
 
 * `FEAT`: add initial snapping when creating associations
diff --git a/package.json b/package.json
index 1c843ed4..aa245083 100644
--- a/package.json
+++ b/package.json
@@ -35,7 +35,9 @@
     }
   ],
   "license": "SEE LICENSE IN LICENSE",
-  "sideEffects": false,
+  "sideEffects": [
+    "*.css"
+  ],
   "devDependencies": {
     "babel-core": "^6.26.0",
     "babel-preset-env": "^1.6.1",