diff --git a/package.json b/package.json
index ca4f36bba85f..26c4121da504 100644
--- a/package.json
+++ b/package.json
@@ -77,7 +77,6 @@
     "magic-string": "^0.19.0",
     "minimatch": "^3.0.3",
     "node-modules-path": "^1.0.0",
-    "node-sass": "^4.3.0",
     "nopt": "^4.0.1",
     "opn": "4.0.2",
     "portfinder": "~1.0.12",
@@ -151,5 +150,8 @@
     "tree-kill": "^1.0.0",
     "ts-node": "^2.0.0",
     "tslint": "^4.0.2"
+  },
+  "optionalDependencies": {
+    "node-sass": "^4.3.0"
   }
 }
diff --git a/packages/@angular/cli/package.json b/packages/@angular/cli/package.json
index 5be43c2c98fa..3697ed2901b4 100644
--- a/packages/@angular/cli/package.json
+++ b/packages/@angular/cli/package.json
@@ -61,7 +61,6 @@
     "lodash": "^4.11.1",
     "minimatch": "^3.0.3",
     "node-modules-path": "^1.0.0",
-    "node-sass": "^4.3.0",
     "nopt": "^4.0.1",
     "opn": "4.0.2",
     "portfinder": "~1.0.12",
@@ -90,6 +89,9 @@
     "webpack-merge": "^2.4.0",
     "zone.js": "^0.7.2"
   },
+  "optionalDependencies": {
+    "node-sass": "^4.3.0"
+  },
   "ember-addon": {
     "paths": [
       "./"
diff --git a/scripts/publish/validate_dependencies.js b/scripts/publish/validate_dependencies.js
index a8c1aa25cf44..ae69faca139b 100644
--- a/scripts/publish/validate_dependencies.js
+++ b/scripts/publish/validate_dependencies.js
@@ -121,6 +121,7 @@ for (const packageName of Object.keys(packages)) {
   const packageJson = JSON.parse(fs.readFileSync(packages[packageName].packageJson, 'utf8'));
   const allDeps = []
     .concat(Object.keys(packageJson['dependencies'] || {}))
+    .concat(Object.keys(packageJson['optionalDependencies'] || {}))
     .concat(Object.keys(packageJson['devDependencies'] || {}))
     .concat(Object.keys(packageJson['peerDependencies'] || {}));
 
@@ -142,6 +143,7 @@ const rootPackageJson = JSON.parse(fs.readFileSync(rootPackagePath, 'utf8'));
 // devDependencies are ignored
 const allRootDeps = []
     .concat(Object.keys(rootPackageJson['dependencies'] || {}))
+    .concat(Object.keys(rootPackageJson['optionalDependencies'] || {}))
     .concat(Object.keys(rootPackageJson['peerDependencies'] || {}));
 
 const internalPackages = Object.keys(packages);