diff --git a/res/Makefile b/res/Makefile
index 9c4bffb6c43d07f20968dcf718f1b94c26258fb1..b0adc07c0ecaba7107baad8d63633315333c3c80 100755
--- a/res/Makefile
+++ b/res/Makefile
@@ -11,11 +11,12 @@
 # the GNU General Public License
 #
 
-MODS=res_adsi.so res_parking.so res_crypto.so
+MODS=res_adsi.so res_parking.so res_crypto.so res_musiconhold.so
 
 CRYPTO_LIBS=-lssl -lcrypto
 
 CFLAGS+=
+CFLAGS+=$(shell [ -f /usr/include/zap.h ] && echo " -DZAPATA_MOH")
 
 all: $(MODS)