diff --git a/src/onboarding/containers/LoginPageContents.tsx b/src/onboarding/containers/LoginPageContents.tsx
index 54a19f95f3..f4b9c09014 100644
--- a/src/onboarding/containers/LoginPageContents.tsx
+++ b/src/onboarding/containers/LoginPageContents.tsx
@@ -174,11 +174,15 @@ class LoginPageContents extends PureComponent<Props> {
     const {email, password} = this.state
 
     const emailError = email === '' ? 'Email is required' : ''
+    const pwlen = new Blob([password]).size
+
     const passwordError = password === '' ? 'Password is required' : ''
+    const passwordLenError = pwlen > 72 ? 'Password is longer than 72 bytes' : ''
 
     const errors: ErrorObject = {
       emailError,
       passwordError,
+      passwordLenError,
     }
 
     const isValid = Object.values(errors).every(error => error === '')