diff --git a/packages/@vue/cli-service/__tests__/Service.spec.js b/packages/@vue/cli-service/__tests__/Service.spec.js
index 2a30c9369..c3d0689f0 100644
--- a/packages/@vue/cli-service/__tests__/Service.spec.js
+++ b/packages/@vue/cli-service/__tests__/Service.spec.js
@@ -23,6 +23,11 @@ const createMockService = (plugins = [], init = true, mode) => {
 
 beforeEach(() => {
   mockPkg({})
+  delete process.env.NODE_ENV
+  delete process.env.BABEL_ENV
+  delete process.env.FOO
+  delete process.env.BAR
+  delete process.env.BAZ
 })
 
 test('env loading', () => {
@@ -35,17 +40,12 @@ test('env loading', () => {
   expect(process.env.BAR).toBe('2')
   expect(process.env.BAZ).toBe('4')
 
-  delete process.env.FOO
-  delete process.env.BAR
-  delete process.env.BAZ
   fs.unlinkSync('/.env.local')
   fs.unlinkSync('/.env')
 })
 
 test('env loading for custom mode', () => {
-  const prevNodeEnv = process.env.NODE_ENV
-  delete process.env.NODE_ENV
-
+  process.env.VUE_CLI_TEST_TESTING_ENV = true
   fs.writeFileSync('/.env', 'FOO=1')
   fs.writeFileSync('/.env.staging', 'FOO=2\nNODE_ENV=production')
   createMockService([], true, 'staging')
@@ -53,8 +53,7 @@ test('env loading for custom mode', () => {
   expect(process.env.FOO).toBe('2')
   expect(process.env.NODE_ENV).toBe('production')
 
-  delete process.env.FOO
-  process.env.NODE_ENV = prevNodeEnv
+  process.env.VUE_CLI_TEST_TESTING_ENV = false
   fs.unlinkSync('/.env')
   fs.unlinkSync('/.env.staging')
 })
diff --git a/packages/@vue/cli-service/lib/Service.js b/packages/@vue/cli-service/lib/Service.js
index 0f29950ab..bd3082248 100644
--- a/packages/@vue/cli-service/lib/Service.js
+++ b/packages/@vue/cli-service/lib/Service.js
@@ -103,14 +103,22 @@ module.exports = class Service {
     // by default, NODE_ENV and BABEL_ENV are set to "development" unless mode
     // is production or test. However the value in .env files will take higher
     // priority.
-    const defaultNodeEnv = (mode === 'production' || mode === 'test')
-      ? mode
-      : 'development'
-    if (process.env.NODE_ENV == null) {
-      process.env.NODE_ENV = defaultNodeEnv
-    }
-    if (process.env.BABEL_ENV == null) {
-      process.env.BABEL_ENV = defaultNodeEnv
+    if (mode) {
+      // always set NODE_ENV during tests
+      // as that is necessary for tests to not be affected by each other
+      const shouldForceDefaultEnv = (
+        process.env.VUE_CLI_TEST &&
+        !process.env.VUE_CLI_TEST_TESTING_ENV
+      )
+      const defaultNodeEnv = (mode === 'production' || mode === 'test')
+        ? mode
+        : 'development'
+      if (shouldForceDefaultEnv || process.env.NODE_ENV == null) {
+        process.env.NODE_ENV = defaultNodeEnv
+      }
+      if (shouldForceDefaultEnv || process.env.BABEL_ENV == null) {
+        process.env.BABEL_ENV = defaultNodeEnv
+      }
     }
   }