diff --git a/packages/@vue/cli/lib/util/__tests__/extendJSConfig.spec.js b/packages/@vue/cli/lib/util/__tests__/extendJSConfig.spec.js
index c998b6ed8f..7eff50cd7b 100644
--- a/packages/@vue/cli/lib/util/__tests__/extendJSConfig.spec.js
+++ b/packages/@vue/cli/lib/util/__tests__/extendJSConfig.spec.js
@@ -61,3 +61,21 @@ module.exports = config`
 module.exports = config`
   )
 })
+
+test(`with extra assignment expression`, () => {
+  const value = {
+    foo: true
+  }
+  const source =
+`process.env.VUE_APP_TEST = 'test'
+module.exports = {
+  bar: 123
+}`
+  expect(extend(value, source)).toMatch(
+    `process.env.VUE_APP_TEST = 'test'
+module.exports = {
+  bar: 123,
+  foo: true
+}`
+  )
+})
diff --git a/packages/@vue/cli/lib/util/extendJSConfig.js b/packages/@vue/cli/lib/util/extendJSConfig.js
index 1559b853fe..17d13603e4 100644
--- a/packages/@vue/cli/lib/util/extendJSConfig.js
+++ b/packages/@vue/cli/lib/util/extendJSConfig.js
@@ -7,7 +7,8 @@ module.exports = function extendJSConfig (value, source) {
   const ast = recast.parse(source)
 
   recast.types.visit(ast, {
-    visitAssignmentExpression ({ node }) {
+    visitAssignmentExpression (path) {
+      const { node } = path
       if (
         node.left.type === 'MemberExpression' &&
         node.left.object.name === 'module' &&
@@ -21,6 +22,7 @@ module.exports = function extendJSConfig (value, source) {
         }
         return false
       }
+      this.traverse(path)
     }
   })