diff --git a/Makefile.defs b/Makefile.defs
index abb39fce..de61d69e 100644
--- a/Makefile.defs
+++ b/Makefile.defs
@@ -242,6 +242,10 @@ export cfg-dir bin-dir modules-dir audio-dir lib-dir ser-cfg-dir doc-dir man-dir
 export bin-target cfg-target modules-target audio-target ser-cfg-target lib-target
 export INSTALL TAR INSTALL-TOUCH INSTALL-CFG INSTALL-BIN INSTALL-MODULES INSTALL-DOC INSTALL-AUDIO
 
+export USE_SPANDSP LIBSPANDSP_STATIC LIBSPANDSP_LDIR
+export USE_LIBSAMPLERATE
+export WITH_ZRTP
+
 endif  # ifeq ($(makefile_defs, 1)
 
 mk-install-dirs: $(DESTDIR)$(cfg-target) \