diff --git a/lib/primitives/address.js b/lib/primitives/address.js
index 0bedf746..20ad7a84 100644
--- a/lib/primitives/address.js
+++ b/lib/primitives/address.js
@@ -246,18 +246,21 @@ Address.prototype.toBech32 = function toBech32(network) {
  */
 
 Address.prototype.fromString = function fromString(addr, network) {
-  let hrp;
-
   assert(typeof addr === 'string');
+  assert(addr.length > 0);
+  assert(addr.length <= 100);
 
+  // If the address is mixed case,
+  // it can only ever be base58.
+  if (isMixedCase(addr))
+    return this.fromBase58(addr, network);
+
+  // Otherwise, it's most likely bech32.
   try {
-    hrp = addr.substring(0, 2).toLowerCase();
-    network = Network.fromBech32(hrp, network);
+    return this.fromBech32(addr, network);
   } catch (e) {
     return this.fromBase58(addr, network);
   }
-
-  return this.fromBech32(addr, network);
 };
 
 /**
@@ -873,6 +876,29 @@ Address.getType = function getType(prefix, network) {
   }
 };
 
+/*
+ * Helpers
+ */
+
+function isMixedCase(str) {
+  let upper = false;
+  let lower = false;
+
+  for (let i = 0; i < str.length; i++) {
+    let ch = str.charCodeAt(i);
+
+    if (ch & 32)
+      upper = true;
+    else
+      lower = true;
+
+    if (upper && lower)
+      return true;
+  }
+
+  return false;
+}
+
 /*
  * Expose
  */
diff --git a/lib/protocol/networks.js b/lib/protocol/networks.js
index ab6109fa..f08b89b2 100644
--- a/lib/protocol/networks.js
+++ b/lib/protocol/networks.js
@@ -14,7 +14,7 @@
 const BN = require('../crypto/bn');
 
 const network = exports;
-let main, testnet, regtest, segnet4, simnet;
+let main, testnet, regtest, simnet;
 
 /**
  * Network type list.
@@ -23,7 +23,7 @@ let main, testnet, regtest, segnet4, simnet;
  * @default
  */
 
-network.types = ['main', 'testnet', 'regtest', 'segnet4', 'simnet'];
+network.types = ['main', 'testnet', 'regtest', 'simnet'];
 
 /**
  * Mainnet
@@ -815,168 +815,6 @@ regtest.selfConnect = true;
 
 regtest.requestMempool = true;
 
-/*
- * segnet4
- */
-
-segnet4 = network.segnet4 = {};
-
-segnet4.type = 'segnet4';
-
-segnet4.seeds = [
-  '104.243.38.34',
-  '37.34.48.17'
-];
-
-segnet4.magic = 0xc4a1abdc;
-
-segnet4.port = 28901;
-
-segnet4.checkpointMap = {};
-segnet4.lastCheckpoint = 0;
-
-segnet4.halvingInterval = 210000;
-
-segnet4.genesis = {
-  version: 1,
-  hash: 'b291211d4bb2b7e1b7a4758225e69e50104091a637213d033295c010f55ffb18',
-  prevBlock: '0000000000000000000000000000000000000000000000000000000000000000',
-  merkleRoot: '3ba3edfd7a7b12b27ac72c3e67768f617fc81bc3888a51323a9fb8aa4b1e5e4a',
-  time: 1452831101,
-  bits: 503447551,
-  nonce: 0,
-  height: 0
-};
-
-segnet4.genesisBlock =
-  '0100000000000000000000000000000000000000000000000000000000000000000000'
-  + '003ba3edfd7a7b12b27ac72c3e67768f617fc81bc3888a51323a9fb8aa4b1e5e4a7d71'
-  + '9856ffff011e0000000001010000000100000000000000000000000000000000000000'
-  + '00000000000000000000000000ffffffff4d04ffff001d0104455468652054696d6573'
-  + '2030332f4a616e2f32303039204368616e63656c6c6f72206f6e206272696e6b206f66'
-  + '207365636f6e64206261696c6f757420666f722062616e6b73ffffffff0100f2052a01'
-  + '000000434104678afdb0fe5548271967f1a67130b7105cd6a828e03909a67962e0ea1f'
-  + '61deb649f6bc3f4cef38c4f35504e51ec112de5c384df7ba0b8d578a4c702b6bf11d5f'
-  + 'ac00000000';
-
-segnet4.pow = {
-  // 512x lower min difficulty than mainnet
-  limit: new BN(
-    '000001ffffffffffffffffffffffffffffffffffffffffffffffffffffffffff',
-    'hex'
-  ),
-  bits: 503447551,
-  chainwork: new BN(
-    '0000000000000000000000000000000000000000000000000000000000800040',
-    'hex'
-  ),
-  targetTimespan: 14 * 24 * 60 * 60,
-  targetSpacing: 10 * 60,
-  retargetInterval: 2016,
-  targetReset: true,
-  noRetargeting: false
-};
-
-segnet4.block = {
-  bip34height: 8,
-  bip34hash: '6c48386dc7c460defabb5640e28b6510a5f238cdbe6756c2976a7e0913000000',
-  bip65height: 8,
-  bip65hash: '6c48386dc7c460defabb5640e28b6510a5f238cdbe6756c2976a7e0913000000',
-  bip66height: 8,
-  bip66hash: '6c48386dc7c460defabb5640e28b6510a5f238cdbe6756c2976a7e0913000000',
-  pruneAfterHeight: 1000,
-  keepBlocks: 10000,
-  maxTipAge: 7 * 24 * 60 * 60,
-  slowHeight: 50000
-};
-
-segnet4.bip30 = {};
-
-segnet4.activationThreshold = 108;
-
-segnet4.minerWindow = 144;
-
-segnet4.deployments = {
-  csv: {
-    name: 'csv',
-    bit: 0,
-    startTime: 1456790400, // March 1st, 2016
-    timeout: 1493596800, // May 1st, 2017
-    threshold: -1,
-    window: -1,
-    required: false,
-    force: true
-  },
-  segwit: {
-    name: 'segwit',
-    bit: 1,
-    startTime: 0,
-    timeout: 0xffffffff,
-    threshold: -1,
-    window: -1,
-    required: true,
-    force: false
-  },
-  segsignal: {
-    name: 'segsignal',
-    bit: 4,
-    startTime: 0xffffffff,
-    timeout: 0xffffffff,
-    threshold: 269,
-    window: 336,
-    required: false,
-    force: false
-  },
-  testdummy: {
-    name: 'testdummy',
-    bit: 28,
-    startTime: 1199145601, // January 1, 2008
-    timeout: 1230767999, // December 31, 2008
-    threshold: -1,
-    window: -1,
-    required: false,
-    force: true
-  }
-};
-
-segnet4.deploys = [
-  segnet4.deployments.csv,
-  segnet4.deployments.segwit,
-  segnet4.deployments.segsignal,
-  segnet4.deployments.testdummy
-];
-
-segnet4.keyPrefix = {
-  privkey: 0x9e,
-  xpubkey: 0x053587cf,
-  xprivkey: 0x05358394,
-  xpubkey58: '2793',
-  xprivkey58: '2791',
-  coinType: 1
-};
-
-segnet4.addressPrefix = {
-  pubkeyhash: 0x1e,
-  scripthash: 0x32,
-  witnesspubkeyhash: 0x04,
-  witnessscripthash: 0x29,
-  bech32: 'sg'
-};
-
-segnet4.requireStandard = false;
-
-segnet4.rpcPort = 28902;
-
-segnet4.minRelay = 1000;
-
-segnet4.feeRate = 20000;
-
-segnet4.maxFeeRate = 60000;
-
-segnet4.selfConnect = false;
-
-segnet4.requestMempool = true;
-
 /*
  * Simnet (btcd)
  */