diff --git a/packages/cli/src/CredentialsHelper.ts b/packages/cli/src/CredentialsHelper.ts
index a5dee733f2..d9ee2b6baf 100644
--- a/packages/cli/src/CredentialsHelper.ts
+++ b/packages/cli/src/CredentialsHelper.ts
@@ -66,6 +66,12 @@ export class CredentialsHelper extends ICredentialsHelper {
 	async updateCredentials(name: string, type: string, data: ICredentialDataDecryptedObject): Promise<void> {
 		const credentials = await this.getCredentials(name, type);
 
+		if (Db.collections!.Credentials === null) {
+			// The first time executeWorkflow gets called the Database has
+			// to get initialized first
+			await Db.init();
+		}
+
 		credentials.setData(data, this.encryptionKey);
 		const newCredentialsData = credentials.getDataToSave() as ICredentialsDb;
 
@@ -75,7 +81,12 @@ export class CredentialsHelper extends ICredentialsHelper {
 		// TODO: also add user automatically depending on who is logged in, if anybody is logged in
 
 		// Save the credentials in DB
-		await Db.collections.Credentials!.save(newCredentialsData);
+		const findQuery = {
+			name,
+			type,
+		};
+
+		await Db.collections.Credentials!.update(findQuery, newCredentialsData);
 	}
 
 }
diff --git a/packages/cli/src/Server.ts b/packages/cli/src/Server.ts
index 1d82c4d807..365bb1765b 100644
--- a/packages/cli/src/Server.ts
+++ b/packages/cli/src/Server.ts
@@ -969,7 +969,7 @@ class App {
 				return ResponseHelper.sendErrorResponse(res, errorResponse);
 			}
 
-			savedCredentialsData.oauthTokenData = JSON.stringify(oauthToken.data);
+			savedCredentialsData.oauthTokenData = oauthToken.data;
 			_.unset(savedCredentialsData, 'csrfSecret');
 
 			credentials.setData(savedCredentialsData, encryptionKey);
diff --git a/packages/core/src/NodeExecuteFunctions.ts b/packages/core/src/NodeExecuteFunctions.ts
index 2c13b2c389..69dd2c92e1 100644
--- a/packages/core/src/NodeExecuteFunctions.ts
+++ b/packages/core/src/NodeExecuteFunctions.ts
@@ -36,8 +36,8 @@ import {
 } from 'n8n-workflow';
 
 import * as clientOAuth2 from 'client-oauth2';
-import { get, unset } from 'lodash';
-import * as express from "express";
+import { get } from 'lodash';
+import * as express from 'express';
 import * as path from 'path';
 import { OptionsWithUri } from 'request';
 import * as requestPromise from 'request-promise-native';
@@ -126,8 +126,13 @@ export function requestOAuth(this: IAllExecuteFunctions, credentialsType: string
 		throw new Error('OAuth credentials not connected!');
 	}
 
-	const oAuthClient = new clientOAuth2({});
-	const oauthTokenData = JSON.parse(credentials.oauthTokenData as string);
+	const oAuthClient = new clientOAuth2({
+		clientId: credentials.clientId as string,
+		clientSecret: credentials.clientSecret as string,
+		accessTokenUri: credentials.accessTokenUrl as string,
+	});
+
+	const oauthTokenData = credentials.oauthTokenData as clientOAuth2.Data;
 	const token = oAuthClient.createToken(oauthTokenData);
 
 	// Signs the request by adding authorization headers or query parameters depending
@@ -142,9 +147,7 @@ export function requestOAuth(this: IAllExecuteFunctions, credentialsType: string
 				// Token is probably not valid anymore. So try refresh it.
 				const newToken = await token.refresh();
 
-				const newCredentialsData = newToken.data;
-				unset(newCredentialsData, 'csrfSecret');
-				unset(newCredentialsData, 'oauthTokenData');
+				credentials.oauthTokenData = newToken.data;
 
 				// Find the name of the credentials
 				if (!node.credentials || !node.credentials[credentialsType]) {
@@ -153,7 +156,7 @@ export function requestOAuth(this: IAllExecuteFunctions, credentialsType: string
 				const name = node.credentials[credentialsType];
 
 				// Save the refreshed token
-				await additionalData.credentialsHelper.updateCredentials(name, credentialsType, newCredentialsData);
+				await additionalData.credentialsHelper.updateCredentials(name, credentialsType, credentials);
 
 				// Make the request again with the new token
 				const newRequestOptions = newToken.sign(requestOptions as clientOAuth2.RequestObject);