diff --git a/src/Stott.Optimizely.RobotsHandler.Test/Llms/LlmsTextControllerTests.cs b/src/Stott.Optimizely.RobotsHandler.Test/Llms/LlmsTextControllerTests.cs
index 6fb0f7e..0dd2887 100644
--- a/src/Stott.Optimizely.RobotsHandler.Test/Llms/LlmsTextControllerTests.cs
+++ b/src/Stott.Optimizely.RobotsHandler.Test/Llms/LlmsTextControllerTests.cs
@@ -71,7 +71,7 @@ public async Task Index_WhenCalled_ReturnsRobotsContent()
         var contentResult = result as ContentResult;
         Assert.That(contentResult, Is.Not.Null);
         Assert.That(contentResult.Content, Is.EqualTo(robotsContent));
-        Assert.That(contentResult.ContentType, Is.EqualTo("text/plain"));
+        Assert.That(contentResult.ContentType, Is.EqualTo("text/plain; charset=utf-8"));
         Assert.That(contentResult.StatusCode, Is.EqualTo(200));
     }
 }
diff --git a/src/Stott.Optimizely.RobotsHandler.Test/Robots/RobotsTextControllerTests.cs b/src/Stott.Optimizely.RobotsHandler.Test/Robots/RobotsTextControllerTests.cs
index 5211f3a..f8082d2 100644
--- a/src/Stott.Optimizely.RobotsHandler.Test/Robots/RobotsTextControllerTests.cs
+++ b/src/Stott.Optimizely.RobotsHandler.Test/Robots/RobotsTextControllerTests.cs
@@ -71,7 +71,7 @@ public async Task Index_WhenCalled_ReturnsRobotsContent()
         var contentResult = result as ContentResult;
         Assert.That(contentResult, Is.Not.Null);
         Assert.That(contentResult.Content, Is.EqualTo(robotsContent));
-        Assert.That(contentResult.ContentType, Is.EqualTo("text/plain"));
+        Assert.That(contentResult.ContentType, Is.EqualTo("text/plain; charset=utf-8"));
         Assert.That(contentResult.StatusCode, Is.EqualTo(200));
     }
 }
diff --git a/src/Stott.Optimizely.RobotsHandler/Llms/LlmsTextController.cs b/src/Stott.Optimizely.RobotsHandler/Llms/LlmsTextController.cs
index 4b5f85a..2c5ba12 100644
--- a/src/Stott.Optimizely.RobotsHandler/Llms/LlmsTextController.cs
+++ b/src/Stott.Optimizely.RobotsHandler/Llms/LlmsTextController.cs
@@ -37,7 +37,7 @@ public async Task<IActionResult> Index()
             return new ContentResult
             {
                 Content = llmsContent,
-                ContentType = "text/plain",
+                ContentType = "text/plain; charset=utf-8",
                 StatusCode = 200
             };
         }
diff --git a/src/Stott.Optimizely.RobotsHandler/Robots/RobotsTextController.cs b/src/Stott.Optimizely.RobotsHandler/Robots/RobotsTextController.cs
index c50b654..9f6b547 100644
--- a/src/Stott.Optimizely.RobotsHandler/Robots/RobotsTextController.cs
+++ b/src/Stott.Optimizely.RobotsHandler/Robots/RobotsTextController.cs
@@ -31,7 +31,7 @@ public async Task<IActionResult> Index()
             return new ContentResult
             {
                 Content = robotsContent,
-                ContentType = "text/plain",
+                ContentType = "text/plain; charset=utf-8",
                 StatusCode = 200
             };
         }