diff --git a/packages/type-params/src/decode/value/index.ts b/packages/type-params/src/decode/value/index.ts
index afff3eed25..c37b29d1ee 100644
--- a/packages/type-params/src/decode/value/index.ts
+++ b/packages/type-params/src/decode/value/index.ts
@@ -5,11 +5,12 @@
 import { EncodingVersions, Param$Decoded, Param$Type } from '../../types';
 import { Decoder } from '../types';
 
-import sizes from '@polkadot/primitives/sizes';
+import defaultSizes from '@polkadot/primitives/sizes';
 import toU8a from '@polkadot/util/u8a/toU8a';
 import isNull from '@polkadot/util/is/null';
 import isUndefined from '@polkadot/util/is/undefined';
 
+import sizes from '../../sizes';
 import accountId from './accountId';
 import bool from './bool';
 import bn from './bn';
@@ -37,8 +38,11 @@ export default function decodeValue (decode: Decoder, type: Param$Type, _input:
       case 'AccountId':
         return accountId(input, version, isStorage);
 
+      case 'AccountIndex':
+        return bn(input, sizes.AccountIndex.get(version) || defaultSizes.AccountIndex);
+
       case 'Balance':
-        return bn(input, sizes.Balance);
+        return bn(input, sizes.Balance.get(version) || defaultSizes.Balance);
 
       case 'BlockNumber':
       case 'Gas':
@@ -72,9 +76,6 @@ export default function decodeValue (decode: Decoder, type: Param$Type, _input:
       case 'Hash':
         return u8a(input, 256, 0);
 
-      case 'AccountIndex':
-        return bn(input, sizes.AccountIndex);
-
       case 'KeyValue':
       case 'StorageKeyValue':
         return keyValue(input);
diff --git a/packages/type-params/src/types.d.ts b/packages/type-params/src/types.d.ts
index a5a2355254..475934f464 100644
--- a/packages/type-params/src/types.d.ts
+++ b/packages/type-params/src/types.d.ts
@@ -27,7 +27,7 @@ export type ExtrinsicDecoded = {
 
 export type BlockExtrinsicDecoded = {
   address: string,
-  nonce: BN,
+  accountIndex: BN,
   extrinsic: SectionItem<Extrinsics>,
   params: Array<any>,
   signature: Uint8Array
diff --git a/packages/type-primitives/src/json/block/decode.spec.js b/packages/type-primitives/src/json/block/decode.spec.js
new file mode 100644
index 0000000000..47fff23148
--- /dev/null
+++ b/packages/type-primitives/src/json/block/decode.spec.js
@@ -0,0 +1,42 @@
+// Copyright 2017-2018 @polkadot/primitives authors & contributors
+// This software may be modified and distributed under the terms
+// of the ISC license. See the LICENSE file for details.
+
+import decode from './decode';
+
+const blockPoc1 = {
+  block: {
+    extrinsics: [
+      [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 0, 36, 241, 242, 90, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
+    ],
+    header: {
+      digest: {
+        logs: []
+      },
+      extrinsicsRoot: '0xcfc906dc1496e190742daefd8ec378a0a901c134d176178f6bbbaeea407b3649',
+      number: 1,
+      parentHash: '0x6c5a31dc701c2a01a3f985da4da5faae19dc205ea212a5b1e4271e3e358271cc',
+      stateRoot: '0x71abf5a507b6cf7a94d5cbfd8b4a1a809167a0044994acb420f891ff18f296d8'
+    }
+  },
+  justification: {
+    hash: '0xa04cab547ca4ef9ff13c1c489a8620994968035a7f07ef9d507226530c8dd81d',
+    round_number: 1,
+    signatures: [
+      ['0x82c39b31a2b79a90f8e66e7a77fdb85a4ed5517f2ae39f6a80565e8ecae85cf5', '0xa681bd611800ede4637f2500315a850ffa8b9202640f0bed06125eb5fb10216c7f8bc4a4a0057a53807242144f2411c26bf84df91e7d62373a8cb7453973010e'],
+      ['0x063d7787ebca768b7445dfebe7d62cbb1625ff4dba288ea34488da266dd6dca5', '0x5710dfbbbb17e1661d7cc0bcf879e8da9ba9255fae15603b35b8079a30f20547f882eaab8ff959ed85cb410718fda102c010420281b5cbef64e5d4e3147c3b0f'],
+      ['0x4de37a07567ebcbf8c64568428a835269a566723687058e017b6d69db00a77e7', '0x95a6fd0eca0f36c560d27fc437433a1bfe3787c98f59515922394c8c51c500f13976cac28c79af22488cb0f9b123d933e4eb0eaf563d3b9672f6ae281e581708']
+    ]
+  }
+};
+
+describe('blockDecode', () => {
+  it('decodes poc-1 blocks properly', () => {
+    expect(
+      decode(blockPoc1).extrinsics[0].extrinsic
+    ).toMatchObject({
+      name: 'set',
+      section: 'timestamp'
+    });
+  });
+});
diff --git a/packages/type-primitives/src/json/extrinsic/decode.spec.js b/packages/type-primitives/src/json/extrinsic/decode.spec.js
index 018b536ad7..11136d0547 100644
--- a/packages/type-primitives/src/json/extrinsic/decode.spec.js
+++ b/packages/type-primitives/src/json/extrinsic/decode.spec.js
@@ -16,6 +16,10 @@ const extrinsics = [
   ])
 ];
 
+const poc1 = new Uint8Array([
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 0, 36, 241, 242, 90, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+]);
+
 describe('extrinsic', () => {
   extrinsics.forEach((extrinsic, index) => {
     it(`decodes the extrinsic - ${index}`, () => {
@@ -24,4 +28,22 @@ describe('extrinsic', () => {
       expect(decoded).toBeDefined();
     });
   });
+
+  it('decodes poc-1 extrinsic', () => {
+    expect(
+      decode(poc1).extrinsic
+    ).toMatchObject({
+      name: 'set',
+      section: 'timestamp'
+    });
+  });
+
+  it('decodes poc-2/latest extrinsic', () => {
+    expect(
+      decode(extrinsics[1]).extrinsic
+    ).toMatchObject({
+      name: 'setHeads',
+      section: 'parachains'
+    });
+  });
 });
diff --git a/packages/type-primitives/src/json/extrinsic/decode.ts b/packages/type-primitives/src/json/extrinsic/decode.ts
index 4a29170ef8..52b28b42c8 100644
--- a/packages/type-primitives/src/json/extrinsic/decode.ts
+++ b/packages/type-primitives/src/json/extrinsic/decode.ts
@@ -2,21 +2,32 @@
 // This software may be modified and distributed under the terms
 // of the ISC license. See the LICENSE file for details.
 
-import { BlockExtrinsicDecoded, ExtrinsicDecoded } from '@polkadot/params/types';
+import { BlockExtrinsicDecoded, ExtrinsicDecoded, EncodingVersions } from '@polkadot/params/types';
 
 import BN from 'bn.js';
 import decoder from '@polkadot/params/decode';
+import ExtError from '@polkadot/util/ext/error';
+import u8aToHex from '@polkadot/util/u8a/toHex';
+
+const VERSIONS: Array<EncodingVersions> = ['latest', 'poc-1'];
 
 export default function extrinsicDecode (extrinsic: Uint8Array): BlockExtrinsicDecoded {
-  const addressDecoded = decoder('AccountId', extrinsic, 'latest');
-  const nonceDecoded = decoder('AccountIndex', extrinsic.subarray(addressDecoded.length), 'latest');
-  const extrinsicDecoded = decoder('Call', extrinsic.subarray(addressDecoded.length + nonceDecoded.length), 'latest');
-  const signature = extrinsic.subarray(addressDecoded.length + nonceDecoded.length + extrinsicDecoded.length);
+  for (let version of VERSIONS) {
+    const addressDecoded = decoder('AccountId', extrinsic, version);
+    const nonceDecoded = decoder('AccountIndex', extrinsic.subarray(addressDecoded.length), version);
+    const extrinsicDecoded = decoder('Call', extrinsic.subarray(addressDecoded.length + nonceDecoded.length), version);
+    const signature = extrinsic.subarray(addressDecoded.length + nonceDecoded.length + extrinsicDecoded.length);
+    const totalLength = addressDecoded.length + nonceDecoded.length + extrinsicDecoded.length + signature.length;
 
-  return {
-    ...(extrinsicDecoded.value as ExtrinsicDecoded),
-    address: addressDecoded.value as string,
-    nonce: nonceDecoded.value as BN,
-    signature
-  };
+    if (totalLength === extrinsic.length) {
+      return {
+        ...(extrinsicDecoded.value as ExtrinsicDecoded),
+        address: addressDecoded.value as string,
+        accountIndex: nonceDecoded.value as BN,
+        signature
+      };
+    }
+  }
+
+  throw new ExtError(`Unable to decode extrinsic: ${u8aToHex(extrinsic)}`);
 }