diff --git a/lib/linguist/languages.yml b/lib/linguist/languages.yml
index 3854ed9a..becdae35 100644
--- a/lib/linguist/languages.yml
+++ b/lib/linguist/languages.yml
@@ -247,6 +247,7 @@ Common Lisp:
   - lisp
   primary_extension: .lisp
   extensions:
+  - .asd
   - .lsp
   - .ny