diff --git a/packages/react-router-config/package.json b/packages/react-router-config/package.json
index 6987a49e46..934ff2818d 100644
--- a/packages/react-router-config/package.json
+++ b/packages/react-router-config/package.json
@@ -16,6 +16,7 @@
   ],
   "main": "index.js",
   "module": "es/index.js",
+  "sideEffects": false,
   "scripts": {
     "build": "node ./tools/build.js",
     "watch": "babel ./modules -d . --ignore __tests__ --watch",
diff --git a/packages/react-router-dom/package.json b/packages/react-router-dom/package.json
index 06834e2cf9..838566db5a 100644
--- a/packages/react-router-dom/package.json
+++ b/packages/react-router-dom/package.json
@@ -29,6 +29,7 @@
   ],
   "main": "index.js",
   "module": "es/index.js",
+  "sideEffects": false,
   "scripts": {
     "build": "node ./tools/build.js",
     "watch": "babel ./modules -d . --ignore __tests__ --watch",
diff --git a/packages/react-router-native/package.json b/packages/react-router-native/package.json
index 9f3086bc9e..85d688b92c 100644
--- a/packages/react-router-native/package.json
+++ b/packages/react-router-native/package.json
@@ -9,6 +9,7 @@
     "Ryan Florence"
   ],
   "main": "main.js",
+  "sideEffects": false,
   "scripts": {
     "start": "node node_modules/react-native/local-cli/cli.js start",
     "clean": "git clean -fdX .",
diff --git a/packages/react-router-redux/package.json b/packages/react-router-redux/package.json
index edb7dd69c5..f1671b89b2 100644
--- a/packages/react-router-redux/package.json
+++ b/packages/react-router-redux/package.json
@@ -19,6 +19,7 @@
   ],
   "main": "index.js",
   "module": "es/index.js",
+  "sideEffects": false,
   "scripts": {
     "build": "node ./tools/build.js",
     "prepublishOnly": "node ./tools/build.js",
diff --git a/packages/react-router/package.json b/packages/react-router/package.json
index e8747725ac..e1c39b2c19 100644
--- a/packages/react-router/package.json
+++ b/packages/react-router/package.json
@@ -25,6 +25,7 @@
   ],
   "main": "index.js",
   "module": "es/index.js",
+  "sideEffects": false,
   "scripts": {
     "build": "node ./tools/build.js",
     "watch": "babel ./modules -d . --ignore __tests__ --watch",