diff --git a/tinc/subnet-up.tmpl b/tinc/subnet-up.tmpl
index 22fea36..c499901 100644
--- a/tinc/subnet-up.tmpl
+++ b/tinc/subnet-up.tmpl
@@ -1,6 +1,6 @@
 #!/bin/ash
 echo "Route up: \$SUBNET weight \$WEIGHT via \$NODE (\$REMOTEADDRESS:\$REMOTEPORT)"
-nonMACChars=`echo \$SUBNET | tr -d "[:digit:]" | tr -d [:ABCDEF]`
+nonMACChars=`echo \$SUBNET | tr -d "[:digit:]" | tr -d [:ABCDEFabcdef]`
 macFile="/tmp/tinc_peer_mac_\$NODE"
 if [ -z "\$nonMACChars" ]; then
   # This subnet is a MAC