From 1a26a15bd47345dcbae5d118cea58311a30a2b05 Mon Sep 17 00:00:00 2001
From: Naresh Bhatia <naresh.archfirst@gmail.com>
Date: Wed, 8 Nov 2017 14:22:46 -0500
Subject: [PATCH] Fixed issue #9027 (#9042)

---
 src/Form/FormControl.js      | 5 ++++-
 src/Form/FormControl.spec.js | 2 +-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/Form/FormControl.js b/src/Form/FormControl.js
index 3cfd8a45617ceb..7598ae32405ef4 100644
--- a/src/Form/FormControl.js
+++ b/src/Form/FormControl.js
@@ -178,7 +178,10 @@ class FormControl extends React.Component<ProvidedProps & Props, State> {
   };
 
   handleBlur = event => {
-    if (this.props.onBlur) {
+    // The event might be undefined.
+    // For instance, a child component might call this hook
+    // when an input is disabled but still having the focus.
+    if (this.props.onBlur && event) {
       this.props.onBlur(event);
     }
     if (this.state.focused) {
diff --git a/src/Form/FormControl.spec.js b/src/Form/FormControl.spec.js
index 2959ba822b0eda..618ced51c9525d 100644
--- a/src/Form/FormControl.spec.js
+++ b/src/Form/FormControl.spec.js
@@ -227,7 +227,7 @@ describe('<FormControl />', () => {
           const handleBlur = spy();
           wrapper.setProps({ onBlur: handleBlur });
           muiFormControlContext.onFocus();
-          muiFormControlContext.onBlur();
+          muiFormControlContext.onBlur({});
           assert.strictEqual(handleBlur.callCount, 1);
         });
       });