diff --git a/app/assets/javascripts/app/lib/app_post/image_service.coffee b/app/assets/javascripts/app/lib/app_post/image_service.coffee
index c68ed442d..8c94b182d 100644
--- a/app/assets/javascripts/app/lib/app_post/image_service.coffee
+++ b/app/assets/javascripts/app/lib/app_post/image_service.coffee
@@ -39,8 +39,8 @@ class App.ImageService
         y = imageHeight / factor
 
       if x is 'auto'# && (y * factor) >= imageWidth
-        factor = imageWidth / y
-        x = imageHeight / factor
+        factor = imageHeight / y
+        x = imageWidth / factor
 
       canvas = document.createElement('canvas')
 
diff --git a/app/views/tests/image_service.html.erb b/app/views/tests/image_service.html.erb
new file mode 100644
index 000000000..555e4f0c6
--- /dev/null
+++ b/app/views/tests/image_service.html.erb
@@ -0,0 +1,15 @@
+
+<link rel="stylesheet" href="/assets/tests/qunit-1.21.0.css">
+<%= javascript_include_tag "/assets/tests/qunit-1.21.0.js", "/assets/tests/image_service.js", nonce: true %>
+
+<style type="text/css">
+body {
+  padding-top: 0px;
+}
+</style>
+
+<script type="text/javascript">
+</script>
+
+<div id="qunit" class="u-dontfold"></div>
+
diff --git a/config/routes/test.rb b/config/routes/test.rb
index cc45d1b7d..69f380570 100644
--- a/config/routes/test.rb
+++ b/config/routes/test.rb
@@ -29,6 +29,7 @@ Zammad::Application.routes.draw do
   match '/tests_ticket_macro',                to: 'tests#ticket_macro',               via: :get
   match '/tests_ticket_selector',             to: 'tests#ticket_selector',            via: :get
   match '/tests_taskbar',                     to: 'tests#taskbar',                    via: :get
+  match '/tests_image_service',               to: 'tests#image_service',              via: :get
   match '/tests_text_module',                 to: 'tests#text_module',                via: :get
   match '/tests_color_object',                to: 'tests#color_object',               via: :get
   match '/tests_kb_video_embeding',           to: 'tests#kb_video_embeding',          via: :get
diff --git a/public/assets/tests/image_service.js b/public/assets/tests/image_service.js
new file mode 100644
index 000000000..83df8bfff
--- /dev/null
+++ b/public/assets/tests/image_service.js
@@ -0,0 +1,13 @@
+// image service
+test('test image resizing with defined height', function(assert) {
+  var async_done = assert.async(1)
+
+  App.ImageService.resize(image_40x30, 'auto', 15, 1, 'image/png', 0.7, function(image, width, height) {
+    equal(width, 20)
+
+    async_done()
+  })
+
+});
+
+var image_40x30 = 'data:image/png;base64,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'
diff --git a/spec/system/js/q_unit_spec.rb b/spec/system/js/q_unit_spec.rb
index 94d05234d..0f675c183 100644
--- a/spec/system/js/q_unit_spec.rb
+++ b/spec/system/js/q_unit_spec.rb
@@ -62,6 +62,10 @@ RSpec.describe 'QUnit', type: :system, authenticated_as: false, set_up: true, we
     it 'Ticket selector' do
       q_unit_tests('ticket_selector')
     end
+
+    it 'Image Service' do
+      q_unit_tests('image_service')
+    end
   end
 
   context 'Form' do