diff --git a/ip/ifcfg b/ip/ifcfg
index ed6960f..fb0fe51 100644
--- a/ip/ifcfg
+++ b/ip/ifcfg
@@ -86,6 +86,10 @@
   fi
   pfx="$ipaddr peer $peer"
 else
+  if [ "$ipaddr" = "" ]; then
+    echo "Missing IP address argument." 1>&2
+    exit 1
+  fi
   if [ "$pfxlen" = "" ]; then
     ABCMaskLen $ipaddr
     pfxlen=$?