diff --git a/lib/block/blockheader.js b/lib/block/blockheader.js
index 2030a0e..cf34ea0 100644
--- a/lib/block/blockheader.js
+++ b/lib/block/blockheader.js
@@ -9,7 +9,7 @@ var Hash = require('../crypto/hash');
 var JSUtil = require('../util/js');
 var $ = require('../util/preconditions');
 
-var GENESIS_BITS = 0x200f0f0f;
+var GENESIS_BITS = 0x2003ffff;
 
 /**
  * Instantiate a BlockHeader from a Buffer, JSON object, or Object with
diff --git a/lib/networks.js b/lib/networks.js
index ba455bb..de2abf0 100644
--- a/lib/networks.js
+++ b/lib/networks.js
@@ -140,7 +140,7 @@ addNetwork({
   xprivkey: 0x0488ade4,
   zaddr: 0x169a,
   zkey: 0xab36,
-  networkMagic: 0x9fee4ed8,
+  networkMagic: 0xf91bacab,
   port: 8233,
   dnsSeeds: [
 //    'seed.bitcoin.sipa.be',
@@ -180,7 +180,7 @@ var testnet = get('testnet');
 
 var TESTNET = {
   PORT: 18233,
-  NETWORK_MAGIC: BufferUtil.integerAsBuffer(0x0c9ed7a2),
+  NETWORK_MAGIC: BufferUtil.integerAsBuffer(0xf99f24b6),
   DNS_SEEDS: [
     'dnsseed.testnet.z.cash',
   ]