diff --git a/app/models/email_address.rb b/app/models/email_address.rb
index 69ae8a066..b027bb1df 100644
--- a/app/models/email_address.rb
+++ b/app/models/email_address.rb
@@ -74,7 +74,7 @@ class EmailAddress < ApplicationRecord
 
   # Returns true if domain belongs to domains list.
   def self.domain_in?(domain, domains)
-    domain = domain.downcase
+    domain = domain.to_s.downcase
     domains = domains.to_s.split(/[\s,]+/) unless domains.is_a?(Array)
     domains.reject(&:blank?).map(&:downcase).any? do |s|
       s.start_with?('.') ? domain.end_with?(s) : domain == s
diff --git a/test/unit/email_address_test.rb b/test/unit/email_address_test.rb
index 9d57beb97..923df897a 100644
--- a/test/unit/email_address_test.rb
+++ b/test/unit/email_address_test.rb
@@ -63,6 +63,12 @@ class EmailAddressTest < ActiveSupport::TestCase
     end
   end
 
+  def test_domain_in_should_not_raise_exception_when_domain_is_nil
+    assert_nothing_raised do
+      assert_not EmailAddress.domain_in?(nil, 'example.com')
+    end
+  end
+
   def test_should_reject_invalid_email
     assert_not EmailAddress.new(address: 'invalid,email@example.com').valid?
   end