diff --git a/build/bakefiles/files.bkl b/build/bakefiles/files.bkl
index fb56f84102..e8c4054036 100644
--- a/build/bakefiles/files.bkl
+++ b/build/bakefiles/files.bkl
@@ -1588,7 +1588,7 @@ IMPORTANT: please read docs/tech/tn0016.txt before modifying this file!
 <set var="MAC_SRC" hints="files">
     src/mac/carbon/accel.cpp
     src/mac/carbon/aga.cpp
-    src/mac/carbon/app.mm
+    src/mac/carbon/app.cpp
     src/mac/carbon/bitmap.cpp
     src/mac/carbon/bmpbuttn.cpp
     src/mac/carbon/brush.cpp