diff --git a/lib/netmask.coffee b/lib/netmask.coffee
index f2ecbf7..44c6263 100644
--- a/lib/netmask.coffee
+++ b/lib/netmask.coffee
@@ -16,6 +16,8 @@ ip2long = (ip) ->
             else
                 # make sure 0 prefixed bytes are parsed as octal
                 byte = parseInt(byte, 8)
+        else if byte and (byte[0] == ' ' or byte[byte.length-1] == ' ')
+            throw new Error('Invalid IP')
         else
             byte = parseInt(byte, 10)
         if isNaN(byte) then throw new Error("Invalid byte: #{byte}")
@@ -25,7 +27,6 @@ ip2long = (ip) ->
         b.unshift(0)
     return (b[0] << 24 | b[1] << 16 | b[2] << 8 | b[3]) >>> 0
 
-
 class Netmask
     constructor: (net, mask) ->
         throw new Error("Missing `net' parameter") unless typeof net is 'string'
diff --git a/test/badnets.coffee b/test/badnets.coffee
index a3d3568..175ddf2 100644
--- a/test/badnets.coffee
+++ b/test/badnets.coffee
@@ -32,6 +32,16 @@ vows.describe('IPs with bytes greater than 255')
         'garbage': shouldFailWithError 'Invalid net'
     .export(module)
 
+vows.describe('Invalid IP format')
+    .addBatch
+        ' 1.2.3.4': shouldFailWithError 'Invalid net'
+        '1. 2.3.4': shouldFailWithError 'Invalid net'
+        '1.2. 3.4': shouldFailWithError 'Invalid net'
+        '1.2.3. 4': shouldFailWithError 'Invalid net'
+        '1.2.3.4 ': shouldFailWithError 'Invalid net'
+        '1 .2.3.4': shouldFailWithError 'Invalid net'
+    .export(module)
+
 vows.describe('Ranges that are a power-of-two big, but are not legal blocks')
     .addBatch
         '218.0.0.0/221.255.255.255': shouldFailWithError 'Invalid mask'