diff --git a/spf-to-ip4-list.rb b/spf-to-ip4-list.rb
index 0eb2fd6..cab54af 100755
--- a/spf-to-ip4-list.rb
+++ b/spf-to-ip4-list.rb
@@ -1,6 +1,7 @@
 #!/usr/bin/env ruby
 
 #require 'spf/query'
+require 'ipaddr'
 
 domain = ARGV[0]
 
@@ -173,7 +174,30 @@ def getAllSpfIp4(domain)
 
 	base_dom["ipv4"].each { |cidr| ipv4 << cidr }
 
-	return ipv4
+	# filter ipv4 list
+	new_ipv4 = []
+	ipv4.each do |ip|
+		if valid_cidr?(ip) or valid_ip_address?(ip)
+			new_ipv4 << ip
+		end
+	end
+
+	return new_ipv4
+end
+
+
+def valid_cidr?(input)
+  IPAddr.new(input)
+  true
+rescue IPAddr::InvalidAddressError
+  false
+end
+
+def valid_ip_address?(input)
+  IPAddr.new(input)
+  true
+rescue IPAddr::InvalidAddressError
+  false
 end
 
 puts getAllSpfIp4(domain)