diff --git a/Makefile.defs b/Makefile.defs
index c723fc45..41aa8d32 100644
--- a/Makefile.defs
+++ b/Makefile.defs
@@ -1,3 +1,6 @@
+ifndef HAVE_MAKEFILE_DEFS
+HAVE_MAKEFILE_DEFS = 1
+
 SVN_REV?=r$(shell svnversion -n .)
 
 #version number
@@ -248,3 +251,4 @@ $(DESTDIR)$(audio-prefix)/$(audio-dir):
 $(DESTDIR)$(doc-prefix)/$(doc-dir):
 	mkdir -p $(DESTDIR)$(doc-prefix)/$(doc-dir)
 
+endif