diff --git a/CHANGELOG.md b/CHANGELOG.md
index 65bdb67..b6b6645 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -15,6 +15,7 @@ This project adheres to [Semantic Versioning](https://semver.org/).
 - Composer script for PHP linting
 
 ### Changed
+- Use `.typoscript` as file extension for TS files (#19)
 - Convert the PHP namespaces to "TTN" (#8)
 - Update the contact email in the CoC document (#6)
 - Switch to the `TTN` PHP vendor namespace (#1, #5)
diff --git a/Configuration/TypoScript/constants.txt b/Configuration/TypoScript/constants.typoscript
similarity index 100%
rename from Configuration/TypoScript/constants.txt
rename to Configuration/TypoScript/constants.typoscript
diff --git a/Configuration/TypoScript/setup.txt b/Configuration/TypoScript/setup.typoscript
similarity index 100%
rename from Configuration/TypoScript/setup.txt
rename to Configuration/TypoScript/setup.typoscript
diff --git a/Tests/Functional/Controller/TeaControllerTest.php b/Tests/Functional/Controller/TeaControllerTest.php
index 98cd024..6b30bdf 100644
--- a/Tests/Functional/Controller/TeaControllerTest.php
+++ b/Tests/Functional/Controller/TeaControllerTest.php
@@ -33,7 +33,7 @@ class TeaControllerTest extends FunctionalTestCase
             1,
             [
                 'EXT:fluid_styled_content/Configuration/TypoScript/setup.txt',
-                'EXT:tea/Configuration/TypoScript/setup.txt',
+                'EXT:tea/Configuration/TypoScript/setup.typoscript',
                 'EXT:tea/Tests/Functional/Controller/Fixtures/Frontend/Basic.typoscript',
             ]
         );