diff --git a/expat/Makefile.in b/expat/Makefile.in
index 1bbbdf9..54c887c 100644
--- a/expat/Makefile.in
+++ b/expat/Makefile.in
@@ -44,7 +44,9 @@
 APIHEADER = $(srcdir)/lib/expat.h $(srcdir)/lib/expat_external.h
 LIBRARY = libexpat.la
 
-INSTALL_ROOT ?= $(DESTDIR)
+ifeq ($(INSTALL_ROOT),)
+INSTALL_ROOT = $(DESTDIR)
+endif
 
 default:  buildlib xmlwf/xmlwf