diff --git a/config/rules.mk b/config/rules.mk
index 9b8f8b3988c..39129e9d089 100644
--- a/config/rules.mk
+++ b/config/rules.mk
@@ -603,7 +603,7 @@ endif #STRICT_CPLUSPLUS_SUFFIX
 
 
 # these rules only apply when the XPIDL compiler is available
-ifdef BUILD_XPIDL
+ifdef USE_XPIDL
 %.h: %.idl $(IDL_COMPILE)
 	$(IDL_COMPILE) -m header -w -I $(DIST)/idl $<
 
diff --git a/modules/libpref/src/Makefile.in b/modules/libpref/src/Makefile.in
index e31284be68c..2c47ef7fb54 100644
--- a/modules/libpref/src/Makefile.in
+++ b/modules/libpref/src/Makefile.in
@@ -42,7 +42,7 @@ EXTRA_LIBS	= $(DIST)/lib/js$(MOZ_BITS)$(VERSION_NUMBER).lib \
 		  $(NULL)
 endif
 
-ifdef BUILD_XPIDL
+ifdef USE_XPIDL
 #temporary hack - eventually nsIPref should live in public
 #but put it here for now so we don't auto-generate the header and loose it
 IDLSRCS		= nsIPref.idl
diff --git a/rdf/base/Makefile.in b/rdf/base/Makefile.in
index 3c686fb280e..b54562063a8 100644
--- a/rdf/base/Makefile.in
+++ b/rdf/base/Makefile.in
@@ -24,7 +24,7 @@ include $(DEPTH)/config/autoconf.mk
 
 DIRS = public src
 
-ifdef BUILD_XPIDL
+ifdef USE_XPIDL
 DIRS += idl
 endif
 
diff --git a/xpcom/tools/Makefile.in b/xpcom/tools/Makefile.in
index 54c9c36b5fd..79c344bc535 100644
--- a/xpcom/tools/Makefile.in
+++ b/xpcom/tools/Makefile.in
@@ -23,8 +23,8 @@ include $(DEPTH)/config/autoconf.mk
 
 DIRS = registry
 
-ifdef BUILD_XPIDL 
+#ifdef BUILD_XPIDL 
 DIRS += xpidl 
-endif 
+#endif 
 
 include $(topsrcdir)/config/rules.mk
diff --git a/xpcom/tools/makefile.win b/xpcom/tools/makefile.win
index fcf2597d5c5..f49dfe777b6 100644
--- a/xpcom/tools/makefile.win
+++ b/xpcom/tools/makefile.win
@@ -21,9 +21,9 @@ IGNORE_MANIFEST=1
 
 DIRS = windows \
        registry \
-!ifdef BUILD_XPIDL 
        xpidl \
-!endif 
        $(NULL)
 
+# removed !ifdef BUILD_XPIDL above...
+
 include <$(DEPTH)\config\rules.mak>
diff --git a/xpfe/AppCores/idl/Makefile.in b/xpfe/AppCores/idl/Makefile.in
index 5b96c95fe1d..719fc21cb77 100644
--- a/xpfe/AppCores/idl/Makefile.in
+++ b/xpfe/AppCores/idl/Makefile.in
@@ -22,7 +22,7 @@ VPATH		= @srcdir@
 
 include $(DEPTH)/config/autoconf.mk
 
-ifdef BUILD_XPIDL
+ifdef USE_XPIDL
 IDLSRCS =	\
 	nsIDOMBaseAppCore.idl	\
 	nsIDOMWindow.idl	\