diff --git a/packages/default-theme/package.json b/packages/default-theme/package.json
index c0b546408..ba59704b9 100644
--- a/packages/default-theme/package.json
+++ b/packages/default-theme/package.json
@@ -23,6 +23,7 @@
     "style/index.js"
   ],
   "style": "style/index.css",
+  "styleModule": "style/index.js",
   "repository": {
     "type": "git",
     "url": "https://github.com/jupyterlab/lumino.git"
diff --git a/packages/dragdrop/package.json b/packages/dragdrop/package.json
index cf7fdd69b..35e44041b 100644
--- a/packages/dragdrop/package.json
+++ b/packages/dragdrop/package.json
@@ -30,6 +30,7 @@
   "module": "dist/index.es6",
   "types": "types/index.d.ts",
   "style": "style/index.css",
+  "styleModule": "style/index.js",
   "scripts": {
     "api": "api-extractor run --local --verbose",
     "build": "tsc --build && rollup -c",
diff --git a/packages/widgets/package.json b/packages/widgets/package.json
index c92a2fc5a..9627f467f 100644
--- a/packages/widgets/package.json
+++ b/packages/widgets/package.json
@@ -30,6 +30,7 @@
   "module": "dist/index.es6",
   "types": "types/index.d.ts",
   "style": "style/index.css",
+  "styleModule": "style/index.js",
   "scripts": {
     "api": "api-extractor run --local --verbose",
     "build": "tsc --build && rollup -c",