diff --git a/lib/linguist/languages.yml b/lib/linguist/languages.yml
index 15a135e1..ca077c97 100644
--- a/lib/linguist/languages.yml
+++ b/lib/linguist/languages.yml
@@ -1626,6 +1626,7 @@ Tcl:
   primary_extension: .tcl
   extensions:
   - .adp
+  - .tm
 
 Tcsh:
   type: programming