diff --git a/lib/linguist/languages.yml b/lib/linguist/languages.yml
index 8a916d48..8342948b 100644
--- a/lib/linguist/languages.yml
+++ b/lib/linguist/languages.yml
@@ -936,6 +936,7 @@ TeX:
   - .sty
   - .tex
   - .toc
+  - .dtx
 
 Text:
   type: data