diff --git a/routes/_utils/ajax.js b/routes/_utils/ajax.js
index dd6ca14..6594355 100644
--- a/routes/_utils/ajax.js
+++ b/routes/_utils/ajax.js
@@ -12,7 +12,7 @@ export async function post(url, body) {
 export function paramsString(paramsObject) {
   let params = new URLSearchParams()
   Object.keys(paramsObject).forEach(key => {
-    params.set(key, paramsObject[value])
+    params.set(key, paramsObject[key])
   })
   return params.toString()
 }
diff --git a/routes/_utils/mastodon/oauth.js b/routes/_utils/mastodon/oauth.js
index 9ff75b1..bb7b4e6 100644
--- a/routes/_utils/mastodon/oauth.js
+++ b/routes/_utils/mastodon/oauth.js
@@ -1,35 +1,34 @@
 const WEBSITE = 'https://pinafore.social'
-const REDIRECT_URI = (typeof location !== 'undefined' ? location.origin : 'https://pinafore.social') + '/settings/instances'
 const SCOPES = 'read write follow'
 const CLIENT_NAME = 'Pinafore'
 import { post, get, paramsString } from '../ajax'
 
-export function registerApplication(instanceName) {
+export function registerApplication(instanceName, redirectUri) {
   const url = `https://${instanceName}/api/v1/apps`
   return post(url, {
       client_name: CLIENT_NAME,
-      redirect_uris: REDIRECT_URI,
+      redirect_uris: redirectUri,
       scopes: SCOPES,
       website: WEBSITE
   })
 }
 
-export function generateAuthLink(instanceName, clientId) {
+export function generateAuthLink(instanceName, clientId, redirectUri) {
   let params = paramsString({
     'client_id': clientId,
-    'redirect_uri': REDIRECT_URI,
+    'redirect_uri': redirectUri,
     'response_type': 'code',
     'scope': SCOPES
   })
   return `https://${instanceName}/oauth/authorize?${params}`
 }
 
-export function getAccessTokenFromAuthCode(instanceName, clientId, clientSecret, code) {
+export function getAccessTokenFromAuthCode(instanceName, clientId, clientSecret, code, redirectUri) {
   let url = `https://${instanceName}/oauth/token`
   return post(url, {
     client_id: clientId,
     client_secret: clientSecret,
-    redirect_uri: REDIRECT_URI,
+    redirect_uri: redirectUri,
     grant_type: 'authorization_code',
     code: code
   })
diff --git a/routes/settings/instances/add.html b/routes/settings/instances/add.html
index b51a569..92ca4fc 100644
--- a/routes/settings/instances/add.html
+++ b/routes/settings/instances/add.html
@@ -53,6 +53,9 @@
   import { store } from '../../_utils/store'
   import { goto } from 'sapper/runtime.js'
 
+  const REDIRECT_URI = (typeof location !== 'undefined' ?
+      location.origin : 'https://pinafore.social') + '/settings/instances/add'
+
   export default {
     oncreate: function () {
       if (process.browser) {
@@ -75,14 +78,18 @@
         let instanceName = this.store.get('instanceNameInSearch')
         instanceName = instanceName.replace(/^https?:\/\//, '').replace('/$', '')
         // TODO: show toast error if you're already logged into this instance
-        let instanceData = await (await registerApplication(instanceName)).json()
+        let instanceData = await registerApplication(instanceName, REDIRECT_URI)
         // TODO: handle error
         this.store.set({
           currentRegisteredInstanceName: instanceName,
           currentRegisteredInstance: instanceData
         })
         this.store.save()
-        let oauthUrl = generateAuthLink(instanceName, instanceData.client_id)
+        let oauthUrl = generateAuthLink(
+          instanceName,
+          instanceData.client_id,
+          REDIRECT_URI
+        )
         document.location.href = oauthUrl
       },
       onReceivedOauthCode: async function(code) {
@@ -92,7 +99,8 @@
           currentRegisteredInstanceName,
           currentRegisteredInstance.client_id,
           currentRegisteredInstance.client_secret,
-          code
+          code,
+          REDIRECT_URI
         )
         // TODO: handle error
         let loggedInInstances = this.store.get('loggedInInstances')