diff --git a/lib/protocol/network.js b/lib/protocol/network.js
index 62e8fdb8c..265c1aac3 100644
--- a/lib/protocol/network.js
+++ b/lib/protocol/network.js
@@ -132,6 +132,9 @@ class Network {
     if (typeof options === 'string')
       options = networks[options];
 
+    if (options instanceof Object)
+      assert(!options.type, 'Unknown network.');
+
     assert(options, 'Unknown network.');
 
     if (Network[options.type])