diff --git a/app/javascript/app/modules/international-phone-formatter.js b/app/javascript/app/modules/international-phone-formatter.js
index 2b3ee0b47db..6f4376a3a46 100644
--- a/app/javascript/app/modules/international-phone-formatter.js
+++ b/app/javascript/app/modules/international-phone-formatter.js
@@ -1,6 +1,8 @@
 import { Formatter } from 'field-kit';
 import { asYouType as AsYouType } from 'libphonenumber-js';
 
+const INTERNATIONAL_CODE_REGEX = /^\+\d{1,3} /;
+
 const fixCountryCodeSpacing = (text, countryCode) => {
   // If the text is `+123456`, make it `+123 456`
   if (text[countryCode.length + 1] !== ' ') {
@@ -29,6 +31,15 @@ const getFormattedTextData = (text) => {
   };
 };
 
+const changeRemovesInternationalCode = (current, previous) => {
+  if (previous.text.match(INTERNATIONAL_CODE_REGEX) &&
+     !current.text.match(INTERNATIONAL_CODE_REGEX)
+  ) {
+    return true;
+  }
+  return false;
+};
+
 const cursorPosition = (formattedTextData) => {
   // If the text is `(23 )` the cursor goes after the 3
   const match = formattedTextData.text.match(/\d[^\d]*$/);
@@ -53,10 +64,7 @@ class InternationalPhoneFormatter extends Formatter {
     const formattedTextData = getFormattedTextData(change.proposed.text);
     const previousFormattedTextData = getFormattedTextData(change.current.text);
 
-    if (previousFormattedTextData.template &&
-      !formattedTextData.template &&
-      change.inserted.text.length === 1
-    ) {
+    if (changeRemovesInternationalCode(formattedTextData, previousFormattedTextData)) {
       return false;
     }
 
diff --git a/spec/features/two_factor_authentication/sign_in_spec.rb b/spec/features/two_factor_authentication/sign_in_spec.rb
index afe7918bb1c..593cea03382 100644
--- a/spec/features/two_factor_authentication/sign_in_spec.rb
+++ b/spec/features/two_factor_authentication/sign_in_spec.rb
@@ -143,6 +143,26 @@
 
         expect(find('#user_phone_form_phone').value).to include '+81'
       end
+
+      scenario 'does not allow the user to remove the international code after entering it', :js do
+        sign_in_before_2fa
+        fill_in 'Phone', with: '+81 54 354 3643'
+
+        input = find('#user_phone_form_phone')
+        input.send_keys(*([:backspace] * input.value.length))
+
+        expect(input.value).to eq('+81 ')
+      end
+
+      scenario 'allows a user to continue typing even if a number is invalid', :js do
+        sign_in_before_2fa
+        select 'United States of America +1', from: 'International code'
+
+        input = find('#user_phone_form_phone')
+        input.send_keys('12345678901234567890')
+
+        expect(input.value).to eq('+1 2345678901234567890')
+      end
     end
   end