diff --git a/src/components/IntlTelInput.js b/src/components/IntlTelInput.js
index 7d06ed369..e35a5fc3d 100644
--- a/src/components/IntlTelInput.js
+++ b/src/components/IntlTelInput.js
@@ -1257,14 +1257,16 @@ class IntlTelInput extends Component {
   }
 
   render() {
-    this.wrapperClass[this.props.containerClassName] = true
     const inputClass = this.props.inputClassName
     const wrapperStyle = Object.assign({}, this.props.style || {})
 
     this.wrapperClass['allow-dropdown'] = this.allowDropdown
     this.wrapperClass.expanded = this.state.showDropdown
 
-    const wrapperClass = classNames(this.wrapperClass)
+    const wrapperClass = classNames(
+      this.wrapperClass,
+      this.props.containerClassName
+    )
 
     const titleTip = this.selectedCountryData
       ? `${this.selectedCountryData.name}: +${this.selectedCountryData.dialCode}`
diff --git a/src/components/__tests__/IntlTelInput.test.js b/src/components/__tests__/IntlTelInput.test.js
new file mode 100644
index 000000000..2ca02093a
--- /dev/null
+++ b/src/components/__tests__/IntlTelInput.test.js
@@ -0,0 +1,20 @@
+import React from 'react'
+import { shallow } from 'enzyme'
+
+import IntlTelInput from '../IntlTelInput'
+
+describe('Style customization', () => {
+  it('correctly applies user-supplied classes on outer container', () => {
+    const component = shallow(<IntlTelInput />)
+    const mockClass = 'mock-class-1'
+    component.setProps({ containerClassName: mockClass })
+    expect(component.props().className).toMatchInlineSnapshot(
+      `"allow-dropdown mock-class-1"`
+    )
+    const otherMockClass = 'mock-class-2'
+    component.setProps({ containerClassName: otherMockClass })
+    expect(component.props().className).toMatchInlineSnapshot(
+      `"allow-dropdown mock-class-2"`
+    )
+  })
+})