--- a/mailnews/Makefile.in
+++ b/mailnews/Makefile.in
@@ -39,28 +39,31 @@ DEPTH		= ..
 topsrcdir	= @top_srcdir@
 srcdir		= @srcdir@
 VPATH		= @srcdir@
 
 include $(DEPTH)/config/autoconf.mk
 
 MODULE       = mailnews
 
-PARALLEL_DIRS	= base/search/src db/msgdb db/gloda news local mime compose imap addrbook import extensions
+PARALLEL_DIRS	+= base/search/src db/msgdb db/gloda news local mime compose imap addrbook import
+
+# extensions (e.g. palmsync) can depend of things built in other dirs
+DIRS	+= extensions
 
 ifeq ($(OS_ARCH),WINNT)
 ifndef GNU_CC
 PARALLEL_DIRS	+= mapi/mapiDLL mapi/mapihook
 endif
 endif
 
 ifdef MOZ_STATIC_MAIL_BUILD
-DIRS = build
+DIRS += build
 else
-DIRS = base/build
+DIRS += base/build
 endif
 
 PREF_JS_EXPORTS = $(srcdir)/mailnews.js
 
 DEFINES += -DOS_ARCH=$(OS_ARCH) \
            -DMOZ_WIDGET_TOOLKIT=$(MOZ_WIDGET_TOOLKIT) \
            $(NULL)