diff --git a/.gitignore b/.gitignore
index 952bf5dc4b..0c17d4d3f0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -11,6 +11,7 @@ tmp/
 .env.test.local
 .env.production.local
 .npmrc
+.rpt2_cache
 cc-test-reporter
 lerna-debug.log*
 npm-debug.log*
diff --git a/packages/types/src/codec/Compact.ts b/packages/types/src/codec/Compact.ts
index a40209022e..3bf7bcae24 100644
--- a/packages/types/src/codec/Compact.ts
+++ b/packages/types/src/codec/Compact.ts
@@ -2,7 +2,7 @@
 // This software may be modified and distributed under the terms
 // of the Apache-2.0 license. See the LICENSE file for details.
 
-import { AnyNumber, Constructor, InterfaceTypes } from '../types';
+import { AnyNumber, Codec, Constructor, InterfaceTypes } from '../types';
 
 import BN from 'bn.js';
 import { bnToBn, compactAddLength, compactFromU8a, compactStripLength, compactToU8a, hexToBn, isBn, isHex, isNumber, isString } from '@polkadot/util';
@@ -10,13 +10,13 @@ import { DEFAULT_BITLENGTH } from '@polkadot/util/compact/defaults';
 
 import { typeToConstructor } from './utils';
 import { UIntBitLength } from './AbstractInt';
-import CodecDate from './Date';
-import UInt from './UInt';
 import Base from './Base';
 
-// List of codec types that are compact-encodable
-export const COMPACT_ENCODABLE = [UInt, CodecDate];
-export type CompactEncodable = UInt | CodecDate; // FIXME is there a way to do it not-manually from the array?
+export interface CompactEncodable extends Codec {
+  bitLength (): UIntBitLength;
+  toBn (): BN;
+  toNumber (): number;
+}
 
 /**
  * @name Compact
diff --git a/packages/types/src/primitive/Null.ts b/packages/types/src/primitive/Null.ts
index 1bad426d23..f4bffa251e 100644
--- a/packages/types/src/primitive/Null.ts
+++ b/packages/types/src/primitive/Null.ts
@@ -5,9 +5,6 @@
 import { Codec, IHash } from '../types';
 
 import { isNull } from '@polkadot/util';
-import { blake2AsU8a } from '@polkadot/util-crypto';
-
-import createType from '../codec/createType';
 
 /**
  * @name Null
@@ -26,7 +23,7 @@ export default class Null implements Codec {
    * @description returns a hash of the contents
    */
   public get hash (): IHash {
-    return createType('Hash', blake2AsU8a(this.toU8a(), 256));
+    throw new Error('.hash is not implemented on Null');
   }
 
   /**
diff --git a/packages/types/src/scripts/interfacesTs.ts b/packages/types/src/scripts/interfacesTs.ts
index 0cfc6dc4ff..c7a7edb827 100644
--- a/packages/types/src/scripts/interfacesTs.ts
+++ b/packages/types/src/scripts/interfacesTs.ts
@@ -12,7 +12,7 @@ import interfaces from '../../../type-jsonrpc/src';
 import { ClassOfUnsafe, getTypeDef } from '../codec/createType';
 import * as codecClasses from '../codec';
 import AbstractInt from '../codec/AbstractInt';
-import { COMPACT_ENCODABLE } from '../codec/Compact';
+import UInt from '../codec/UInt';
 import Vec from '../codec/Vec';
 import * as definitions from '../interfaces/definitions';
 import * as primitiveClasses from '../primitive';
@@ -70,10 +70,7 @@ function isChildClass (Parent: Constructor<any>, Child: Constructor<any>): boole
 }
 
 function isCompactEncodable (Child: Constructor<any>): boolean {
-  // @ts-ignore AbstractInt is abstract, we shouldn't isChildClass it here, but it works
-  return Object.values(COMPACT_ENCODABLE).some((CompactEncodable): boolean =>
-    isChildClass(CompactEncodable, Child)
-  );
+  return isChildClass(UInt, Child);
 }
 
 // helper to generate a `export interface <Name> extends <Base> {<Body>}