diff --git a/modules.d/40network/net-genrules.sh b/modules.d/40network/net-genrules.sh
index 867abcf0..3bb5d807 100755
--- a/modules.d/40network/net-genrules.sh
+++ b/modules.d/40network/net-genrules.sh
@@ -10,7 +10,8 @@ fix_bootif() {
     macaddr=${macaddr%:}
     # strip hardware type field from pxelinux
     [ -n "${macaddr%??:??:??:??:??:??}" ] && macaddr=${macaddr#??:}
-    echo $macaddr
+    # return macaddr with lowercase alpha characters expected by udev
+    echo $macaddr | sed 'y/ABCDEF/abcdef/'
 }
 
 # Don't continue if we don't need network