diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4a3b31f80c62..7c25ca8db217 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,6 @@
 ## Changelog
 ##### Unreleased
+- Added `sideEffects` field to `core-js-pure` `package.json` for better tree shaking, [#1117](https://github.com/zloirock/core-js/issues/1117)
 - Dropped `semver` dependency from `core-js-compat`
   - `semver` package (ironically) added [a breaking change and dropped NodeJS 8 support in the minor `7.1` version](https://github.com/npm/node-semver/commit/d61f828e64260a0a097f26210f5500), after that `semver` in `core-js-compat` was pinned to `7.0` since for avoiding breaking changes it should support NodeJS 8. However, since `core-js-compat` is usually used with other packages that use `semver` dependency, it causes multiple duplication of `semver` in dependencies. So I decided to remove `semver` dependency and replace it with a couple of simple helpers.
 - Added Bun 0.1.6-0.1.10 compat data
diff --git a/packages/core-js-pure/package.json b/packages/core-js-pure/package.json
index aa8b3b86153e..4a856b63f424 100644
--- a/packages/core-js-pure/package.json
+++ b/packages/core-js-pure/package.json
@@ -7,6 +7,7 @@
     "url": "https://github.com/zloirock/core-js.git"
   },
   "main": "index.js",
+  "sideEffects": ["./modules/*.js"],
   "funding": {
     "type": "opencollective",
     "url": "https://opencollective.com/core-js"