diff --git a/lerna.json b/lerna.json
index 36010f4dd..97d9b36d8 100644
--- a/lerna.json
+++ b/lerna.json
@@ -10,5 +10,5 @@
   "packages": [
     "packages/*"
   ],
-  "version": "0.16.6"
+  "version": "0.17.0"
 }
diff --git a/packages/util-crypto/package.json b/packages/util-crypto/package.json
index b8fe149dd..00c92da5a 100644
--- a/packages/util-crypto/package.json
+++ b/packages/util-crypto/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@polkadot/util-crypto",
-  "version": "0.16.6",
+  "version": "0.17.0",
   "description": "A collection of useful crypto utilities for @polkadot",
   "main": "index.js",
   "keywords": [
diff --git a/packages/util-keyring/package.json b/packages/util-keyring/package.json
index 9e95e9ce8..7725c16cb 100644
--- a/packages/util-keyring/package.json
+++ b/packages/util-keyring/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@polkadot/util-keyring",
-  "version": "0.16.6",
+  "version": "0.17.0",
   "description": "Keyring management",
   "main": "index.js",
   "engines": {
@@ -31,8 +31,8 @@
     "test": "echo \"Tests only available from root wrapper\""
   },
   "dependencies": {
-    "@polkadot/util": "^0.16.6",
-    "@polkadot/util-crypto": "^0.16.6",
+    "@polkadot/util": "^0.17.0",
+    "@polkadot/util-crypto": "^0.17.0",
     "babel-runtime": "^6.26.0"
   }
 }
diff --git a/packages/util-keyring/src/testing.js b/packages/util-keyring/src/testing.js
index e245a8d01..65d83dc5d 100644
--- a/packages/util-keyring/src/testing.js
+++ b/packages/util-keyring/src/testing.js
@@ -11,19 +11,25 @@ type TestKeyring = {
 
 const createKeyring = require('./index');
 
+function padSeed (seed: string): string {
+  return seed.length < 32
+    ? padSeed(`${seed} `)
+    : seed;
+}
+
 const SEEDS = {
   alice:
-    'Alice                           ',
+    padSeed('Alice'),
   bob:
-    'Bob                             ',
+    padSeed('Bob'),
   charlie:
-    'Charlie                         ',
+    padSeed('Charlie'),
   dave:
-    'Dave                            ',
+    padSeed('Dave'),
   eve:
-    'Eve                             ',
+    padSeed('Eve'),
   ferdie:
-    'Ferdie                          ',
+    padSeed('Ferdie'),
   one:
     '12345678901234567890123456789012',
   two:
diff --git a/packages/util-keyring/src/testing.spec.js b/packages/util-keyring/src/testing.spec.js
new file mode 100644
index 000000000..49b0a014f
--- /dev/null
+++ b/packages/util-keyring/src/testing.spec.js
@@ -0,0 +1,11 @@
+// Copyright 2017-2018 Jaco Greeff
+// This software may be modified and distributed under the terms
+// of the ISC license. See the LICENSE file for details.
+
+describe('testing', () => {
+  it('creates without failing', () => {
+    expect(
+      require('./testing')
+    ).toBeDefined();
+  });
+});
diff --git a/packages/util-rlp/package.json b/packages/util-rlp/package.json
index 0e5046152..394e9b22c 100644
--- a/packages/util-rlp/package.json
+++ b/packages/util-rlp/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@polkadot/util-rlp",
-  "version": "0.16.6",
+  "version": "0.17.0",
   "description": "RLP encoding and decoding",
   "main": "index.js",
   "keywords": [
@@ -29,7 +29,7 @@
     "test": "echo \"Tests only available from root wrapper\""
   },
   "dependencies": {
-    "@polkadot/util": "^0.16.6",
+    "@polkadot/util": "^0.17.0",
     "babel-runtime": "^6.26.0"
   },
   "devDependencies": {
diff --git a/packages/util-rlp/src/encoder/array.js b/packages/util-rlp/src/encoder/array.js
index 4c76d2f68..d6cf2030e 100644
--- a/packages/util-rlp/src/encoder/array.js
+++ b/packages/util-rlp/src/encoder/array.js
@@ -11,18 +11,10 @@ const encodeLength = require('./length');
 
 // flowlint-next-line unclear-type:off
 module.exports = function encodeArray (encoder: EncodeFunc, input: any): Uint8Array {
-  const output = [];
+  const encoded = u8aConcat.apply(null, input.map(encoder));
 
-  for (let i = 0; i < input.length; i++) {
-    output.push(
-      encoder(input[i])
-    );
-  }
-
-  const encoded = u8aConcat(output);
-
-  return u8aConcat([
+  return u8aConcat(
     encodeLength(encoded.length, 192),
     encoded
-  ]);
+  );
 };
diff --git a/packages/util-rlp/src/encoder/u8a.js b/packages/util-rlp/src/encoder/u8a.js
index 981836007..dfa20c99b 100644
--- a/packages/util-rlp/src/encoder/u8a.js
+++ b/packages/util-rlp/src/encoder/u8a.js
@@ -14,8 +14,8 @@ module.exports = function encodeU8a (encoder: EncodeFunc, input: Uint8Array): Ui
     return input;
   }
 
-  return u8aConcat([
+  return u8aConcat(
     encodeLength(input.length, 128),
     input
-  ]);
+  );
 };
diff --git a/packages/util-triehash/package.json b/packages/util-triehash/package.json
index ddb20493c..ecd262783 100644
--- a/packages/util-triehash/package.json
+++ b/packages/util-triehash/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@polkadot/util-triehash",
-  "version": "0.16.6",
+  "version": "0.17.0",
   "description": "Creation of triehash values",
   "main": "index.js",
   "keywords": [
@@ -29,9 +29,9 @@
     "test": "echo \"Tests only available from root wrapper\""
   },
   "dependencies": {
-    "@polkadot/util": "^0.16.6",
-    "@polkadot/util-crypto": "^0.16.6",
-    "@polkadot/util-rlp": "^0.16.6",
+    "@polkadot/util": "^0.17.0",
+    "@polkadot/util-crypto": "^0.17.0",
+    "@polkadot/util-rlp": "^0.17.0",
     "babel-runtime": "^6.26.0"
   }
 }
diff --git a/packages/util/package.json b/packages/util/package.json
index 5af220542..08198dd7a 100644
--- a/packages/util/package.json
+++ b/packages/util/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@polkadot/util",
-  "version": "0.16.6",
+  "version": "0.17.0",
   "description": "A collection of useful utilities for @polkadot",
   "main": "index.js",
   "keywords": [
diff --git a/packages/util/src/u8a/concat.js b/packages/util/src/u8a/concat.js
index 5f9400c7c..319cec9b0 100644
--- a/packages/util/src/u8a/concat.js
+++ b/packages/util/src/u8a/concat.js
@@ -5,20 +5,21 @@
 
 /**
   @name u8aConcat
-  @signature u8aConcat (values: Array<Uint8Array>): Uint8Array
+  @signature u8aConcat (...values: Array<Uint8Array>): Uint8Array
   @summary Creates a concatenated Uint8Array from the inputs.
   @description
     Concatenates the input arrays into a single `UInt8Array`.
   @example
     import { u8aConcat } from '@polkadot/util';
 
-    u8aConcat([
+    u8aConcat(
       new Uint8Array([1, 2, 3]),
       new Uint8Array([4, 5, 6])
-    ]); // [1, 2, 3, 4, 5, 6]
+    ); // [1, 2, 3, 4, 5, 6]
 */
-module.exports = function u8aConcat (list: Array<Uint8Array>): Uint8Array {
+module.exports = function u8aConcat (...list: Array<Uint8Array>): Uint8Array {
   const length = list.reduce((total, item) => total + item.length, 0);
+  const result = new Uint8Array(length);
   let offset = 0;
 
   return list.reduce((result, item) => {
@@ -26,5 +27,5 @@ module.exports = function u8aConcat (list: Array<Uint8Array>): Uint8Array {
     offset += item.length;
 
     return result;
-  }, new Uint8Array(length));
+  }, result);
 };
diff --git a/packages/util/src/u8a/concat.spec.js b/packages/util/src/u8a/concat.spec.js
index 569351979..5980348ec 100644
--- a/packages/util/src/u8a/concat.spec.js
+++ b/packages/util/src/u8a/concat.spec.js
@@ -7,11 +7,11 @@ const { u8aConcat } = require('./index');
 describe('u8aConcat', () => {
   it('concatenates arrays', () => {
     expect(
-      u8aConcat([
+      u8aConcat(
         new Uint8Array([1, 2, 3, 4]),
         new Uint8Array([5, 6]),
         new Uint8Array([7, 8, 9])
-      ])
+      )
     ).toEqual(
       new Uint8Array([1, 2, 3, 4, 5, 6, 7, 8, 9])
     );