diff --git a/lib/linguist/languages.yml b/lib/linguist/languages.yml
index 7bd8072d..77da5506 100644
--- a/lib/linguist/languages.yml
+++ b/lib/linguist/languages.yml
@@ -419,7 +419,7 @@ CLIPS:
 CMake:
   extensions:
   - .cmake
-  - .in
+  - .cmake.in
   filenames:
   - CMakeLists.txt
   ace_mode: text