Index: /trunk/src/VBox/Frontends/VirtualBox/Makefile.kmk
===================================================================
--- /trunk/src/VBox/Frontends/VirtualBox/Makefile.kmk	(revision 26654)
+++ /trunk/src/VBox/Frontends/VirtualBox/Makefile.kmk	(revision 26655)
@@ -41,5 +41,7 @@
 # Build new VirtualBox FE/Qt4 GUI runtime core.
 # Currently its not used, you can build it for developing purposes.
+ifneq ($(KBUILD_TARGET),darwin)
 #VBOX_WITH_NEW_RUNTIME_CORE := 1
+endif
 
 #
@@ -169,4 +171,7 @@
 ifdef VBOX_WITH_ICHAT_THEATER
  VirtualBox_DEFS.darwin += VBOX_WITH_ICHAT_THEATER
+endif
+ifdef VBOX_WITH_NEW_RUNTIME_CORE
+ VirtualBox_DEFS += VBOX_WITH_NEW_RUNTIME_CORE
 endif
 ifneq ($(KBUILD_TYPE),release)