diff --git a/app/models/screened_ip_address.rb b/app/models/screened_ip_address.rb
index 7941543b33b..974e5baf798 100644
--- a/app/models/screened_ip_address.rb
+++ b/app/models/screened_ip_address.rb
@@ -26,6 +26,21 @@ class ScreenedIpAddress < ActiveRecord::Base
     self.errors.add(:ip_address, :invalid)
   end
 
+  # Return a string with the ip address and mask in standard format. e.g., "127.0.0.0/8".
+  # Ruby's IPAddr class has no method for getting this.
+  def ip_address_with_mask
+    if ip_address
+      mask = ip_address.instance_variable_get(:@mask_addr).to_s(2).count('1')
+      if mask == 32
+        ip_address.to_s
+      else
+        "#{ip_address.to_s}/#{ip_address.instance_variable_get(:@mask_addr).to_s(2).count('1')}"
+      end
+    else
+      nil
+    end
+  end
+
   def self.match_for_ip_address(ip_address)
     # The <<= operator on inet columns means "is contained within or equal to".
     #
diff --git a/app/serializers/screened_ip_address_serializer.rb b/app/serializers/screened_ip_address_serializer.rb
index 59c95bdfcc1..54e9922d58e 100644
--- a/app/serializers/screened_ip_address_serializer.rb
+++ b/app/serializers/screened_ip_address_serializer.rb
@@ -11,7 +11,7 @@ class ScreenedIpAddressSerializer < ApplicationSerializer
   end
 
   def ip_address
-    object.ip_address.try(:to_s)
+    object.ip_address_with_mask
   end
 
 end
diff --git a/spec/models/screened_ip_address_spec.rb b/spec/models/screened_ip_address_spec.rb
index 6f282a10be2..861ae8946ec 100644
--- a/spec/models/screened_ip_address_spec.rb
+++ b/spec/models/screened_ip_address_spec.rb
@@ -33,6 +33,20 @@ describe ScreenedIpAddress do
     end
   end
 
+  describe "ip_address_with_mask" do
+    it "returns nil when ip_address is nil" do
+      described_class.new.ip_address_with_mask.should be_nil
+    end
+
+    it "returns ip_address without mask if there is no mask" do
+      described_class.new(ip_address: "123.123.23.22").ip_address_with_mask.should == "123.123.23.22"
+    end
+
+    it "returns ip_address with mask" do
+      described_class.new(ip_address: "123.12.0.0/16").ip_address_with_mask.should == "123.12.0.0/16"
+    end
+  end
+
   describe '#watch' do
     context 'ip_address is not being watched' do
       it 'should create a new record' do