diff --git a/package.json b/package.json
index 6cd93bf67..5e94b280d 100644
--- a/package.json
+++ b/package.json
@@ -44,6 +44,7 @@
     "ansi-to-html": "^0.6.3",
     "chalk": "^2.3.0",
     "codemirror": "^5.25.0",
+    "cross-env": "^5.2.0",
     "dashify": "^1.0.0",
     "deep-equal": "^1.0.1",
     "detect-port": "^1.1.1",
@@ -78,8 +79,8 @@
     "rm-modules": "rm -rf node_modules static/node_modules",
     "rm-temp": "rm -rf $TMPDIR/jest* $TMPDIR/react-native-packager*",
     "reset": "yarn cache clean && yarn rm-dist && yarn rm-modules && yarn rm-temp",
-    "start": "NODE_ENV=development node scripts/start-dev-server.js",
-    "build": "yarn rm-dist && NODE_ENV=production node scripts/build-release.js $@",
+    "start": "cross-env NODE_ENV=development node scripts/start-dev-server.js",
+    "build": "yarn rm-dist && cross-env NODE_ENV=production node scripts/build-release.js $@",
     "fix": "eslint . --fix",
     "lint": "eslint . && flow check"
   },
diff --git a/scripts/yarn-install.js b/scripts/yarn-install.js
index d7fd2cc87..fc13cee0c 100644
--- a/scripts/yarn-install.js
+++ b/scripts/yarn-install.js
@@ -7,7 +7,7 @@
 
 const glob = require('glob');
 const path = require('path');
-const {spawn} = require('child_process');
+const {exec} = require('child_process');
 const PACKAGES = ['static', 'src/plugins/*', 'src/fb/plugins/*'];
 const WINDOWS = /^win/.test(process.platform);
 const YARN_PATH =
@@ -36,13 +36,21 @@ Promise.all(
     Promise.all(
       packages.reduce((acc, cv) => acc.concat(cv), []).map(
         pkg =>
-          new Promise(resolve => {
+          new Promise((resolve, reject) => {
             const cwd = pkg.replace('/package.json', '');
-            const yarn = spawn(YARN_PATH, ['--mutex', 'file'], {
-              cwd,
-            });
-            yarn.stderr.on('data', e => console.error(e.toString()));
-            yarn.on('close', code => resolve(code));
+            exec(
+              [YARN_PATH, '--mutex', 'file'].join(' '),
+              {
+                cwd,
+              },
+              (err, stderr, stdout) => {
+                if (err) {
+                  reject(err);
+                } else {
+                  resolve(0);
+                }
+              },
+            );
           }),
       ),
     ),
diff --git a/src/utils/CertificateProvider.js b/src/utils/CertificateProvider.js
index 5739d336b..b753f2be3 100644
--- a/src/utils/CertificateProvider.js
+++ b/src/utils/CertificateProvider.js
@@ -171,7 +171,7 @@ export default class CertificateProvider {
           ),
       );
     }
-    if (os === 'iOS') {
+    if (os === 'iOS' || os === 'windows') {
       fs.writeFileSync(destination + filename, contents);
       return Promise.resolve();
     }
diff --git a/yarn.lock b/yarn.lock
index 96d5f1110..af5965b89 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -1088,6 +1088,13 @@ create-error-class@^3.0.0:
   dependencies:
     capture-stack-trace "^1.0.0"
 
+cross-env@^5.2.0:
+  version "5.2.0"
+  resolved "https://registry.yarnpkg.com/cross-env/-/cross-env-5.2.0.tgz#6ecd4c015d5773e614039ee529076669b9d126f2"
+  dependencies:
+    cross-spawn "^6.0.5"
+    is-windows "^1.0.0"
+
 cross-spawn@^5.0.1, cross-spawn@^5.1.0:
   version "5.1.0"
   resolved "https://registry.yarnpkg.com/cross-spawn/-/cross-spawn-5.1.0.tgz#e8bd0efee58fcff6f8f94510a0a554bbfa235449"
@@ -1096,6 +1103,16 @@ cross-spawn@^5.0.1, cross-spawn@^5.1.0:
     shebang-command "^1.2.0"
     which "^1.2.9"
 
+cross-spawn@^6.0.5:
+  version "6.0.5"
+  resolved "https://registry.yarnpkg.com/cross-spawn/-/cross-spawn-6.0.5.tgz#4a5ec7c64dfae22c3a14124dbacdee846d80cbc4"
+  dependencies:
+    nice-try "^1.0.4"
+    path-key "^2.0.1"
+    semver "^5.5.0"
+    shebang-command "^1.2.0"
+    which "^1.2.9"
+
 cross-unzip@0.0.2:
   version "0.0.2"
   resolved "https://registry.yarnpkg.com/cross-unzip/-/cross-unzip-0.0.2.tgz#5183bc47a09559befcf98cc4657964999359372f"
@@ -2635,7 +2652,7 @@ is-utf8@^0.2.0:
   version "0.2.1"
   resolved "https://registry.yarnpkg.com/is-utf8/-/is-utf8-0.2.1.tgz#4b0da1442104d1b336340e80797e865cf39f7d72"
 
-is-windows@^1.0.2:
+is-windows@^1.0.0, is-windows@^1.0.2:
   version "1.0.2"
   resolved "https://registry.yarnpkg.com/is-windows/-/is-windows-1.0.2.tgz#d1850eb9791ecd18e6182ce12a30f396634bb19d"
 
@@ -3478,6 +3495,10 @@ negotiator@0.6.1:
   version "0.6.1"
   resolved "https://registry.yarnpkg.com/negotiator/-/negotiator-0.6.1.tgz#2b327184e8992101177b28563fb5e7102acd0ca9"
 
+nice-try@^1.0.4:
+  version "1.0.4"
+  resolved "https://registry.yarnpkg.com/nice-try/-/nice-try-1.0.4.tgz#d93962f6c52f2c1558c0fbda6d512819f1efe1c4"
+
 node-fetch@^1.0.1:
   version "1.7.3"
   resolved "https://registry.yarnpkg.com/node-fetch/-/node-fetch-1.7.3.tgz#980f6f72d85211a5347c6b2bc18c5b84c3eb47ef"
@@ -3794,7 +3815,7 @@ path-is-inside@^1.0.1, path-is-inside@^1.0.2:
   version "1.0.2"
   resolved "https://registry.yarnpkg.com/path-is-inside/-/path-is-inside-1.0.2.tgz#365417dede44430d1c11af61027facf074bdfc53"
 
-path-key@^2.0.0:
+path-key@^2.0.0, path-key@^2.0.1:
   version "2.0.1"
   resolved "https://registry.yarnpkg.com/path-key/-/path-key-2.0.1.tgz#411cadb574c5a140d3a4b1910d40d80cc9f40b40"