diff --git a/rtgui/CMakeLists.txt b/rtgui/CMakeLists.txt
index 831f100e7..72df9fba0 100644
--- a/rtgui/CMakeLists.txt
+++ b/rtgui/CMakeLists.txt
@@ -122,8 +122,8 @@ set(NONCLISOURCEFILES
     rgbcurves.cc
     rotate.cc
     rtimage.cc
-	rtsurface.cc
-	rtscalable.cc
+    rtsurface.cc
+    rtscalable.cc
     rtwindow.cc
     saveasdlg.cc
     saveformatpanel.cc