diff --git a/src/kits/interface/interface.src b/src/kits/interface/interface.src
index 0dc9003b8e..c8e945662d 100644
--- a/src/kits/interface/interface.src
+++ b/src/kits/interface/interface.src
@@ -17,6 +17,7 @@ INTERFACE_KIT_SOURCE =
 	RadioButton.cpp
 	Rect.cpp
 	Region.cpp
+	region_helpers.cpp
 	ScrollBar.cpp
 	StatusBar.cpp
 	StringView.cpp