diff --git a/lib/networks.js b/lib/networks.js
index 51062f060..96e6176f2 100644
--- a/lib/networks.js
+++ b/lib/networks.js
@@ -75,7 +75,7 @@ function addNetwork(data) {
   });
 
   _.each(_.values(network), function(value) {
-    if (!_.isObject(value)) {
+    if (!_.isUndefined(value) && !_.isObject(value)) {
       networkMaps[value] = network;
     }
   });
diff --git a/test/networks.js b/test/networks.js
index ddcd07a59..d019479ba 100644
--- a/test/networks.js
+++ b/test/networks.js
@@ -20,7 +20,7 @@ describe('Networks', function() {
       pubkeyhash: 0x10,
       privatekey: 0x90,
       scripthash: 0x08,
-      xpubkey:  0x0278b20e,
+      xpubkey: 0x0278b20e,
       xprivkey: 0x0278ade4,
       networkMagic: 0xe7beb4d4,
       port: 20001,
@@ -40,6 +40,25 @@ describe('Networks', function() {
       }
     }
   });
+  
+  it('should not set a network map for an undefined value', function() {
+    var custom = {
+      name: 'somenet',
+      pubkeyhash: 0x13,
+      privatekey: 0x93,
+      scripthash: 0x11,
+      xpubkey: 0x0278b20f,
+      xprivkey: 0x0278ade5,
+      networkMagic: 0xe7beb4d5,
+      port: 20008,
+      dnsSeeds: [
+        'somenet.localhost'
+      ]
+    };
+    networks.add(custom);
+    var network = networks.get(undefined);
+    should.not.exist(network);
+  });
 
   var constants = ['name', 'alias', 'pubkeyhash', 'scripthash', 'xpubkey', 'xprivkey'];