diff --git a/packages/api/src/promise/index.ts b/packages/api/src/promise/index.ts
index b13963671e..019dfdcd37 100644
--- a/packages/api/src/promise/index.ts
+++ b/packages/api/src/promise/index.ts
@@ -14,10 +14,7 @@ import { isFunction } from '@polkadot/util';
 import ApiBase from '../Base';
 import Combinator, { CombinatorCallback, CombinatorFunction } from './Combinator';
 
-interface RxFn {
-  (...params: Array<any>): Observable<Codec | undefined | null>;
-  isSubscription: boolean;
-}
+type RxFn = (...params: Array<any>) => Observable<Codec | undefined | null>;
 
 /**
  * # @polkadot/api/promise
@@ -196,8 +193,8 @@ export default class ApiPromise extends ApiBase<OnCall> implements ApiPromiseInt
     };
   }
 
-  protected onCall (method: RxFn, params: Array<any>, isSubscription: boolean = false): OnCall {
-    if (!params || params.length === 0 || !isSubscription) {
+  protected onCall (method: RxFn, params: Array<any>, isSubscription?: boolean): OnCall {
+    if (!params || params.length === 0 || isSubscription === false) {
       return method(...params).pipe(first()).toPromise();
     }
 
diff --git a/packages/api/test/e2e/promise-queries.spec.js b/packages/api/test/e2e/promise-queries.spec.js
index 2f70fd3b33..fa5f700fc6 100644
--- a/packages/api/test/e2e/promise-queries.spec.js
+++ b/packages/api/test/e2e/promise-queries.spec.js
@@ -1,7 +1,6 @@
 // Copyright 2017-2019 @polkadot/api authors & contributors
 // This software may be modified and distributed under the terms
 // of the Apache-2.0 license. See the LICENSE file for details.
-// @ts-check
 
 import BN from 'bn.js';
 import testingPairs from '@polkadot/keyring/testingPairs';
diff --git a/packages/api/test/e2e/promise-tx.spec.js b/packages/api/test/e2e/promise-tx.spec.js
index 38aefaf8ab..6df72275b8 100644
--- a/packages/api/test/e2e/promise-tx.spec.js
+++ b/packages/api/test/e2e/promise-tx.spec.js
@@ -1,7 +1,6 @@
 // Copyright 2017-2019 @polkadot/api authors & contributors
 // This software may be modified and distributed under the terms
 // of the Apache-2.0 license. See the LICENSE file for details.
-// @ts-check
 
 import testingPairs from '@polkadot/keyring/testingPairs';
 
@@ -47,7 +46,7 @@ describe.skip('e2e transactions', () => {
   });
 
   it('makes a transfer (signAndSend)', async (done) => {
-    const unsubscribe = await api.tx.balances
+    api.tx.balances
       .transfer('12ghjsRJpeJpUQaCQeHcBv9pRQA3tdcMxeL8cVk9JHWJGHjd', 12345)
       .signAndSend(keyring.dave, ({ events, status, type }) => {
         console.log('Transaction status:', type);
@@ -60,8 +59,9 @@ describe.skip('e2e transactions', () => {
             console.log('\t', phase.toString(), `: ${section}.${method}`, data.toString());
           });
 
-          unsubscribe();
-          done();
+          if (events.length) {
+            done();
+          }
         }
       });
   });
diff --git a/packages/api/test/e2e/rx-queries.spec.js b/packages/api/test/e2e/rx-queries.spec.js
index b607b77da9..13979a7ec8 100644
--- a/packages/api/test/e2e/rx-queries.spec.js
+++ b/packages/api/test/e2e/rx-queries.spec.js
@@ -1,7 +1,6 @@
 // Copyright 2017-2019 @polkadot/api authors & contributors
 // This software may be modified and distributed under the terms
 // of the Apache-2.0 license. See the LICENSE file for details.
-// @ts-check
 
 import { switchMap } from 'rxjs/operators';
 import testingPairs from '@polkadot/keyring/testingPairs';
diff --git a/packages/api/test/e2e/rx-tx.spec.js b/packages/api/test/e2e/rx-tx.spec.js
index 14d28c5fa9..def6f0894b 100644
--- a/packages/api/test/e2e/rx-tx.spec.js
+++ b/packages/api/test/e2e/rx-tx.spec.js
@@ -1,7 +1,6 @@
 // Copyright 2017-2019 @polkadot/api authors & contributors
 // This software may be modified and distributed under the terms
 // of the Apache-2.0 license. See the LICENSE file for details.
-// @ts-check
 
 import { first, switchMap } from 'rxjs/operators';
 import testingPairs from '@polkadot/keyring/testingPairs';
diff --git a/packages/rpc-rx/src/index.ts b/packages/rpc-rx/src/index.ts
index e60d8a25cf..d708db526b 100644
--- a/packages/rpc-rx/src/index.ts
+++ b/packages/rpc-rx/src/index.ts
@@ -4,7 +4,7 @@
 
 import { RpcInterface$Method, RpcInterface$Section } from '@polkadot/rpc-core/types';
 import { ProviderInterface } from '@polkadot/rpc-provider/types';
-import { RpcRxInterface, RpcRxInterface$Events, RpcRxInterface$Section, RpcRxObervable } from './types';
+import { RpcRxInterface, RpcRxInterface$Events, RpcRxInterface$Section } from './types';
 
 import EventEmitter from 'eventemitter3';
 import { BehaviorSubject, Observable, Subscriber, from } from 'rxjs';
@@ -100,27 +100,21 @@ export default class RpcRx implements RpcRxInterface {
       }, ({} as RpcRxInterface$Section));
   }
 
-  private createObservable (subName: string, name: string, section: RpcInterface$Section): RpcRxObervable {
-    const isSubscription = isFunction(section[name].unsubscribe);
-    const fn = isSubscription
-      ? this.createCachedObservable(subName, name, section)
-      : (...params: Array<any>): Observable<any> =>
-          from(
-            section[name]
-              .apply(null, params)
-              .catch((error: Error) => {
-                console.error(error);
-              })
-          );
+  private createObservable (subName: string, name: string, section: RpcInterface$Section): (...params: Array<any>) => Observable<any> {
+    if (isFunction(section[name].unsubscribe)) {
+      return this.createCachedObservable(subName, name, section);
+    }
 
-    const result = fn as RpcRxObervable;
-
-    result.isSubscription = isSubscription;
-
-    return result;
+    return (...params: Array<any>): Observable<any> =>
+      from(
+        section[name]
+          .apply(null, params)
+          .catch((error: Error) => {
+            console.error(error);
+          })
+      );
   }
 
-  // FIXME Memoization as in derive, https://github.com/polkadot-js/api/issues/553
   private createCachedObservable (subName: string, name: string, section: RpcInterface$Section): (...params: Array<any>) => Observable<any> {
     if (!this._cacheMap[subName]) {
       this._cacheMap[subName] = {};
diff --git a/packages/rpc-rx/src/types.ts b/packages/rpc-rx/src/types.ts
index 4b02c793a7..60328d4bdf 100644
--- a/packages/rpc-rx/src/types.ts
+++ b/packages/rpc-rx/src/types.ts
@@ -5,13 +5,10 @@
 import { ReplaySubject, Observable } from 'rxjs';
 import { ProviderInterface$Emitted } from '@polkadot/rpc-provider/types';
 
-export interface RpcRxObervable {
-  (...params: Array<any>): Observable<any> | ReplaySubject<any>;
-  isSubscription: boolean;
-}
+export type RpcRxInterface$Method = (...params: Array<any>) => Observable<any> | ReplaySubject<any>;
 
 export type RpcRxInterface$Section = {
-  [index: string]: RpcRxObervable
+  [index: string]: RpcRxInterface$Method
 };
 
 export type RpcRxInterface$Events = ProviderInterface$Emitted;