diff --git a/build/jam/BuildSetup b/build/jam/BuildSetup
index ed496222ce..858fb0708e 100644
--- a/build/jam/BuildSetup
+++ b/build/jam/BuildSetup
@@ -125,7 +125,9 @@ if $(HAIKU_PACKAGING_ARCH) {
 	KernelArchitectureSetup $(HAIKU_PACKAGING_ARCH) ;
 }
 
-HAIKU_DEFINES = __HAIKU__ ;
+# define primary packaging architecture macro
+HAIKU_DEFINES = __HAIKU_PRIMARY_PACKAGING_ARCH=\\\"$(HAIKU_PACKAGING_ARCH)\\\" ;
+
 HAIKU_LIBSUPC++ = $(HAIKU_LIBSUPC++_$(HAIKU_PACKAGING_ARCH)) ;
 HAIKU_LIBSTDC++ = $(HAIKU_LIBSTDC++_$(HAIKU_PACKAGING_ARCH)) ;