diff --git a/.changeset/witty-carpets-clap.md b/.changeset/witty-carpets-clap.md
new file mode 100644
index 000000000..ce05bef21
--- /dev/null
+++ b/.changeset/witty-carpets-clap.md
@@ -0,0 +1,5 @@
+---
+'@lion/ui': patch
+---
+
+fix(@lion/ui): declare sideEffects in package.json
diff --git a/packages/ui/package.json b/packages/ui/package.json
index 73bc6caba..bf0b7f255 100644
--- a/packages/ui/package.json
+++ b/packages/ui/package.json
@@ -45,6 +45,13 @@
     "types-check-only": "tsc --project tsconfig-check-only.json",
     "types-correct-after-build": "node ./scripts/types-correct-after-build.js"
   },
+  "sideEffects": [
+    "exports/define/**/*.js",
+    "exports/define-helpers/**/*.js",
+    "exports/icon.js",
+    "exports/localize.js",
+    "exports/overlays.js"
+  ],
   "dependencies": {
     "@bundled-es-modules/message-format": "^6.0.4",
     "@open-wc/dedupe-mixin": "^1.3.1",