diff --git a/channels/chan_zap.c b/channels/chan_zap.c
index babaeb7f2816da426f60a3934ce3e4b4b447573f..adc6217c92bf7efb17ec453b7d7434781f0582c6 100644
--- a/channels/chan_zap.c
+++ b/channels/chan_zap.c
@@ -107,7 +107,7 @@ ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
 #define SMDI_MD_WAIT_TIMEOUT 1500 /* 1.5 seconds */
 #endif
 
-#ifndef ZT_SIG_HARDHDLC
+#if !defined(ZT_SIG_EM_E1) || (defined(ZAPATA_PRI) && !defined(ZT_SIG_HARDHDLC))
 #error "Your zaptel is too old.  please update"
 #endif