diff --git a/package/base-files/files/bin/ipcalc.sh b/package/base-files/files/bin/ipcalc.sh
index 27a52d6f83..5d5eac3ea8 100755
--- a/package/base-files/files/bin/ipcalc.sh
+++ b/package/base-files/files/bin/ipcalc.sh
@@ -31,7 +31,11 @@ BEGIN {
 	slpos=index(ARGV[1],"/")
 	if (slpos == 0) {
 		ipaddr=ip2int(ARGV[1])
-		netmask=ip2int(ARGV[2])
+		dotpos=index(ARGV[2],".")
+		if (dotpos == 0)
+			netmask=compl32(2**(32-int(ARGV[2]))-1)
+		else
+			netmask=ip2int(ARGV[2])
 	} else {
 		ipaddr=ip2int(substr(ARGV[1],0,slpos-1))
 		netmask=compl32(2**(32-int(substr(ARGV[1],slpos+1)))-1)