diff --git a/app/ModelSerializers/Summit/Speakers/PresentationSpeakerSerializer.php b/app/ModelSerializers/Summit/Speakers/PresentationSpeakerSerializer.php
index 2e7476088..fdc018f3a 100644
--- a/app/ModelSerializers/Summit/Speakers/PresentationSpeakerSerializer.php
+++ b/app/ModelSerializers/Summit/Speakers/PresentationSpeakerSerializer.php
@@ -394,10 +394,9 @@ protected function checkDataPermissions(PresentationSpeaker $speaker, array $val
         }
         */
 
-        if(!$speaker->isPublicProfileShowTelephoneNumber())
-        {
-            if(isset($values['phone_number'])) $values['phone_number'] = '';
-        }
+        // phone_number is never public regardless of the target speaker's own account
+        // visibility toggle - see policy/profile-data-handling.md Rule 4.
+        if(isset($values['phone_number'])) $values['phone_number'] = '';
 
         return $values;
     }
diff --git a/tests/PresentationSpeakerSerializerTest.php b/tests/PresentationSpeakerSerializerTest.php
new file mode 100644
index 000000000..192a02184
--- /dev/null
+++ b/tests/PresentationSpeakerSerializerTest.php
@@ -0,0 +1,52 @@
+<?php namespace Tests;
+/*
+ * Copyright 2026 OpenStack Foundation
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+use models\oauth2\IResourceServerContext;
+use models\summit\PresentationSpeaker;
+use ModelSerializers\PresentationSpeakerSerializer;
+use Mockery;
+
+/**
+ * Class PresentationSpeakerSerializerTest
+ * @package Tests
+ */
+final class PresentationSpeakerSerializerTest extends TestCase
+{
+    public function tearDown(): void
+    {
+        Mockery::close();
+        parent::tearDown();
+    }
+
+    public function testPhoneNumberIsMaskedInPublicContextEvenWhenSpeakerToggleIsOn()
+    {
+        $speaker = Mockery::mock(PresentationSpeaker::class)->makePartial();
+        $speaker->shouldReceive('hasMember')->andReturn(false);
+        $speaker->shouldReceive('getPhoneNumber')->andReturn('+1-555-0100');
+        // target speaker's own account-level toggle is ON - the exact case that used to leak
+        // the raw phone_number regardless of the requesting caller's identity.
+        $speaker->shouldReceive('isPublicProfileShowTelephoneNumber')->andReturn(true);
+        $speaker->shouldReceive('isPublicProfileShowBio')->andReturn(true);
+        $speaker->shouldReceive('isPublicProfileShowEmail')->andReturn(true);
+        $speaker->shouldReceive('isPublicProfileShowSocialMediaInfo')->andReturn(true);
+        $speaker->shouldReceive('isPublicProfileShowPhoto')->andReturn(true);
+
+        $resource_server_context = Mockery::mock(IResourceServerContext::class);
+        $serializer = new PresentationSpeakerSerializer($speaker, $resource_server_context);
+
+        $values = $serializer->serialize(null, ['phone_number'], ['none']);
+
+        $this->assertSame('', $values['phone_number']);
+    }
+}