diff --git a/packages/type-params/src/types.d.ts b/packages/type-params/src/types.d.ts
index 5b0f6f52ab..a5a2355254 100644
--- a/packages/type-params/src/types.d.ts
+++ b/packages/type-params/src/types.d.ts
@@ -33,10 +33,19 @@ export type BlockExtrinsicDecoded = {
   signature: Uint8Array
 }
 
+export type BlockJustificationDecoded = {
+  hash: Uint8Array,
+  round: BN,
+  signatures: Array<{
+    address: string,
+    signature: Uint8Array
+  }>
+}
+
 export type BlockDecoded = {
   header: Header,
   extrinsics: Array<BlockExtrinsicDecoded>,
-  justification: any
+  justification: BlockJustificationDecoded
 };
 
 export type KeyValue = {
diff --git a/packages/type-primitives/src/json/block/decode.ts b/packages/type-primitives/src/json/block/decode.ts
index 69028ec773..0902a61d94 100644
--- a/packages/type-primitives/src/json/block/decode.ts
+++ b/packages/type-primitives/src/json/block/decode.ts
@@ -9,16 +9,16 @@ import toU8a from '@polkadot/util/u8a/toU8a';
 
 import decodeExtrinsic from '../extrinsic/decode';
 import decodeHeader from '../header/decode';
+import decodeJustification from '../justification/decode';
 
 export default function blockDecode ({ block: { extrinsics, header }, justification }: JsonBlock): BlockDecoded {
   return {
-    // TODO We should decode the justifications (and change type from any)
-    justification,
-    header: decodeHeader(header),
     extrinsics: extrinsics.map((extrinsic) =>
       decodeExtrinsic(
         toU8a(extrinsic as any)
       )
-    )
+    ),
+    header: decodeHeader(header),
+    justification: decodeJustification(justification)
   };
 }
diff --git a/packages/type-primitives/src/json/justification/decode.ts b/packages/type-primitives/src/json/justification/decode.ts
new file mode 100644
index 0000000000..5cba60bcd5
--- /dev/null
+++ b/packages/type-primitives/src/json/justification/decode.ts
@@ -0,0 +1,21 @@
+// 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 { BlockJustificationDecoded } from '@polkadot/params/types';
+import { JsonJustification } from '../types';
+
+import BN from 'bn.js';
+import toU8a from '@polkadot/util/u8a/toU8a';
+import addressEncode from '@polkadot/util-keyring/address/encode';
+
+export default function justificcationDecode ({ hash, round_number, signatures }: JsonJustification): BlockJustificationDecoded {
+  return {
+    hash: toU8a(hash),
+    round: new BN(round_number),
+    signatures: signatures.map(([address, signature]) => ({
+      address: addressEncode(toU8a(address)),
+      signature: toU8a(signature)
+    }))
+  };
+}
diff --git a/packages/type-primitives/src/json/types.d.ts b/packages/type-primitives/src/json/types.d.ts
index e5b378c6c0..36cc2bc19f 100644
--- a/packages/type-primitives/src/json/types.d.ts
+++ b/packages/type-primitives/src/json/types.d.ts
@@ -46,7 +46,11 @@ export type JsonHeader = {
   digest: JsonDigest
 };
 
-export type JsonJustification = {};
+export type JsonJustification = {
+  hash: string,
+  round_number: number,
+  signatures: Array<[string, string]>
+};
 
 export type JsonBlock = {
   block: {