diff --git a/packages/core/utils/package.json b/packages/core/utils/package.json
index 020e994f10b..8505658a841 100644
--- a/packages/core/utils/package.json
+++ b/packages/core/utils/package.json
@@ -45,5 +45,10 @@
   "devDependencies": {
     "@babel/plugin-transform-flow-strip-types": "^7.2.0",
     "random-int": "^1.0.0"
+  },
+  "browser": {
+    "./src/generateCertificate.js": false,
+    "./src/http-server.js": false,
+    "./src/openInBrowser.js": false
   }
 }
diff --git a/packages/core/workers/package.json b/packages/core/workers/package.json
index 423615b53ee..9e460984290 100644
--- a/packages/core/workers/package.json
+++ b/packages/core/workers/package.json
@@ -30,5 +30,10 @@
   },
   "peerDependencies": {
     "@parcel/core": "^2.0.0"
+  },
+  "browser": {
+    "./src/cpuCount.js": false,
+    "./src/process/ProcessWorker.js": false,
+    "./src/threads/ThreadsWorker.js": false
   }
 }