diff --git a/app/helpers/authenticated_url_helper.rb b/app/helpers/authenticated_url_helper.rb
index f549db099..d33d852e0 100644
--- a/app/helpers/authenticated_url_helper.rb
+++ b/app/helpers/authenticated_url_helper.rb
@@ -86,7 +86,7 @@ def add_query_parameters(url, parameters)
       parsed_url = URI.parse url
 
       # Add the given parameters to the query string
-      query_params = CGI.parse(parsed_url.query || '')
+      query_params = CGI.parse(parsed_url.query || '').with_indifferent_access
       query_params.merge!(parameters)
 
       # Add the query string back to the URL
diff --git a/spec/helpers/authenticated_url_helper_spec.rb b/spec/helpers/authenticated_url_helper_spec.rb
new file mode 100644
index 000000000..bc1720322
--- /dev/null
+++ b/spec/helpers/authenticated_url_helper_spec.rb
@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe AuthenticatedUrlHelper do
+  describe '#add_query_parameters' do
+    it 'adds the given parameters to the given url' do
+      expect(described_class.add_query_parameters(root_url, {foo: 'bar'})).to eq(root_url(foo: 'bar'))
+    end
+
+    it 'does not duplicate existing parameters' do
+      expect(described_class.add_query_parameters(root_url(foo: 'bar'), {foo: 'baz'})).to eq(root_url(foo: 'baz'))
+    end
+  end
+end