diff --git a/packages/@uppy/transloadit/src/AssemblyOptions.js b/packages/@uppy/transloadit/src/AssemblyOptions.js
index bfce66c7a..9d1447304 100644
--- a/packages/@uppy/transloadit/src/AssemblyOptions.js
+++ b/packages/@uppy/transloadit/src/AssemblyOptions.js
@@ -19,7 +19,7 @@ function validateParams (params) {
 
   if (!params.auth || !params.auth.key) {
     throw new Error('Transloadit: The `params.auth.key` option is required. ' +
-      'You can find your Transloadit API key at https://transloadit.com/accounts/credentials.')
+      'You can find your Transloadit API key at https://transloadit.com/account/api-settings.')
   }
 }
 
diff --git a/packages/@uppy/transloadit/src/index.js b/packages/@uppy/transloadit/src/index.js
index 6b1b1b1db..0e1965bf7 100644
--- a/packages/@uppy/transloadit/src/index.js
+++ b/packages/@uppy/transloadit/src/index.js
@@ -67,8 +67,13 @@ module.exports = class Transloadit extends Plugin {
     this._onRestored = this._onRestored.bind(this)
     this._getPersistentData = this._getPersistentData.bind(this)
 
+    const hasCustomAssemblyOptions = this.opts.getAssemblyOptions !== defaultOptions.getAssemblyOptions
     if (this.opts.params) {
       AssemblyOptions.validateParams(this.opts.params)
+    } else if (!hasCustomAssemblyOptions) {
+      // Throw the same error that we'd throw if the `params` returned from a
+      // `getAssemblyOptions()` function is null.
+      AssemblyOptions.validateParams(null)
     }
 
     this.client = new Client({