diff --git a/check_source/check_cmake_consistency.py b/check_source/check_cmake_consistency.py
index c1f0a559dde2264996df23bd4654153fb8fce7b5..9833093c68d370c9136e579e092f06b6271b30bd 100755
--- a/check_source/check_cmake_consistency.py
+++ b/check_source/check_cmake_consistency.py
@@ -95,7 +95,7 @@ def is_c_header(filename: str) -> bool:
 
 def is_c(filename: str) -> bool:
     ext = splitext(filename)[1]
-    return (ext in {".c", ".cpp", ".cxx", ".m", ".mm", ".rc", ".cc", ".inl", ".metal"})
+    return (ext in {".c", ".cpp", ".cxx", ".m", ".mm", ".rc", ".cc", ".inl", ".metal", ".msl"})
 
 
 def is_c_any(filename: str) -> bool: