diff --git a/blockcheck.sh b/blockcheck.sh
index e933594..1b1d95a 100755
--- a/blockcheck.sh
+++ b/blockcheck.sh
@@ -156,7 +156,7 @@ check_prerequisites()
 
 	
 	[ -x "$PKTWS" ] && [ -x "$TPWS" ] && [ -x "$MDIG" ] || {
-		echo $PKTWS or $TPWS or $MDIG is not available. run $ZAPRET_BASE/install_bin.sh or make -C \"$ZAPRET_BASE\"
+		echo $PKTWS or $TPWS or $MDIG is not available. run \"$ZAPRET_BASE/install_bin.sh\" or make -C \"$ZAPRET_BASE\"
 		exitp 6
 	}
 
@@ -171,6 +171,10 @@ check_prerequisites()
 				echo ipfw or ipdivert kernel module not loaded
 				exitp 6
 			}
+			[ "$(sysctl -qn net.inet.ip.fw.enable)" = 0 -o "$(sysctl -qn net.inet6.ip6.fw.enable)" = 0 ] && {
+				echo ipfw is disabled. use : ipfw enable firewall
+				exitp 6
+			}
 			;;
 	esac