diff --git a/addons/api/mirage/config.js b/addons/api/mirage/config.js
index 2fd0d4ea1..538df19de 100644
--- a/addons/api/mirage/config.js
+++ b/addons/api/mirage/config.js
@@ -60,7 +60,17 @@ export default function () {
   this.post('/auth-methods');
   this.get('/auth-methods/:id');
   this.patch('/auth-methods/:id');
-  this.del('/auth-methods/:id');
+  this.del('/auth-methods/:id', ({ authMethods }, { params: { id } }) => {
+    const authMethod = authMethods.find(id);
+    const scope = authMethod.scope;
+    authMethod.destroy();
+    // If the primary auth method is deleted, the associated scope's
+    // primary_auth_method_id field should be set to null.
+    if (scope.primary_auth_method_id === id) {
+      scope.update({ primary_auth_method_id: null });
+    }
+    return new Response(204);
+  });
 
   // Auth Method Accounts
   this.get(
diff --git a/ui/admin/app/controllers/scopes/scope/auth-methods/index.js b/ui/admin/app/controllers/scopes/scope/auth-methods/index.js
index c51e1d044..60ae5951c 100644
--- a/ui/admin/app/controllers/scopes/scope/auth-methods/index.js
+++ b/ui/admin/app/controllers/scopes/scope/auth-methods/index.js
@@ -1,7 +1,13 @@
 import Controller from '@ember/controller';
 
 export default class ScopesScopeAuthMethodsIndexController extends Controller {
+  // =attributes
+
+  /**
+   * True if the current scope has a primary auth method set.
+   * @type {boolean}
+   */
   get hasPrimaryAuthMethod() {
-    return this.model.filterBy('isPrimary');
+    return this.scopeModel.primary_auth_method_id;
   }
 }
diff --git a/ui/admin/app/routes/scopes/scope/auth-methods.js b/ui/admin/app/routes/scopes/scope/auth-methods.js
index 81b4347da..fe2f7905b 100644
--- a/ui/admin/app/routes/scopes/scope/auth-methods.js
+++ b/ui/admin/app/routes/scopes/scope/auth-methods.js
@@ -71,7 +71,11 @@ export default class ScopesScopeAuthMethodsRoute extends Route {
   @notifyError(({ message }) => message, { catch: true })
   @notifySuccess('notifications.delete-success')
   async delete(authMethod) {
+    const scopeModel = this.modelFor('scopes.scope');
     await authMethod.destroyRecord();
+    // Reload the scope, since this is where the primary_auth_method_id is
+    // stored.  An auth method deletion could affect this field.
+    await scopeModel.reload();
     await this.replaceWith('scopes.scope.auth-methods');
     this.refresh();
   }
diff --git a/ui/admin/app/routes/scopes/scope/auth-methods/index.js b/ui/admin/app/routes/scopes/scope/auth-methods/index.js
index a7e38aa5a..913b4f8ff 100644
--- a/ui/admin/app/routes/scopes/scope/auth-methods/index.js
+++ b/ui/admin/app/routes/scopes/scope/auth-methods/index.js
@@ -1,3 +1,15 @@
 import Route from '@ember/routing/route';
 
-export default class ScopesScopeAuthMethodsIndexRoute extends Route {}
+export default class ScopesScopeAuthMethodsIndexRoute extends Route {
+  // =methods
+
+  /**
+   * Adds the scope to the controller context.
+   * @param {Controller} controller
+   */
+  setupController(controller) {
+    super.setupController(...arguments);
+    const scopeModel = this.modelFor('scopes.scope');
+    controller.scopeModel = scopeModel;
+  }
+}