diff --git a/addons/mail/static/src/js/document_viewer.js b/addons/mail/static/src/js/document_viewer.js
index 338b5889828..8b6f27b480e 100644
--- a/addons/mail/static/src/js/document_viewer.js
+++ b/addons/mail/static/src/js/document_viewer.js
@@ -44,11 +44,10 @@ var DocumentViewer = Widget.extend({
         this._super.apply(this, arguments);
         this.attachment = _.filter(attachments, function (attachment) {
             var match = attachment.type === 'url' ? attachment.url.match("(youtu|.png|.jpg|.gif)") : attachment.mimetype.match("(image|video|application/pdf|text)");
-
             if (match) {
-                attachment.type = match[1];
+                attachment.fileType = match[1];
                 if (match[1].match("(.png|.jpg|.gif)")) {
-                    attachment.type = 'image';
+                    attachment.fileType = 'image';
                 }
                 if (match[1] === 'youtu') {
                     var youtube_array = attachment.url.split('/');
diff --git a/addons/mail/static/src/xml/thread.xml b/addons/mail/static/src/xml/thread.xml
index be73917a1b5..6d8782cad97 100644
--- a/addons/mail/static/src/xml/thread.xml
+++ b/addons/mail/static/src/xml/thread.xml
@@ -38,9 +38,9 @@
             <t t-set="model" t-value="widget.modelName"/>
             <div class="o_viewer-header">
                 <span class="o_image_caption">
-                    <i class="fa fa-picture-o mr8" t-if="widget.activeAttachment.type == 'image'" role="img" aria-label="Image" title="Image"/>
-                    <i class="fa fa-file-text mr8" t-if="widget.activeAttachment.type == 'application/pdf'" role="img" aria-label="PDF file" title="PDF file"/>
-                    <i class="fa fa-video-camera mr8" t-if="widget.activeAttachment.type == 'video'" role="img" aria-label="Video" title="Video"/>
+                    <i class="fa fa-picture-o mr8" t-if="widget.activeAttachment.fileType == 'image'" role="img" aria-label="Image" title="Image"/>
+                    <i class="fa fa-file-text mr8" t-if="widget.activeAttachment.fileType == 'application/pdf'" role="img" aria-label="PDF file" title="PDF file"/>
+                    <i class="fa fa-video-camera mr8" t-if="widget.activeAttachment.fileType == 'video'" role="img" aria-label="Video" title="Video"/>
                     <t t-esc="widget.activeAttachment.name"/>
                     <a role="button" href="#" class="o_download_btn ml8 small" data-toggle="tooltip" data-placement="right" title="Download"><i class="fa fa-fw fa-download" role="img" aria-label="Download"/></a>
                 </span>
@@ -48,19 +48,19 @@
             </div>
             <div class="o_viewer_img_wrapper">
                 <div class="o_viewer_zoomer">
-                    <div t-if="widget.activeAttachment.type == 'image'" class="o_loading_img text-center">
+                    <div t-if="widget.activeAttachment.fileType == 'image'" class="o_loading_img text-center">
                         <i class="fa fa-circle-o-notch fa-spin text-gray-light fa-3x fa-fw" role="img" aria-label="Loading" title="Loading"/>
                     </div>
-                    <img t-if="widget.activeAttachment.type === 'image'" class="o_viewer_img" t-attf-src="/web/image/#{widget.activeAttachment.id}?unique=1&amp;signature=#{widget.activeAttachment.checksum}&amp;model=#{model}" alt="Viewer"/>
-                    <iframe t-if="widget.activeAttachment.type == 'application/pdf'" class="mt32 o_viewer_pdf"  t-attf-src="/web/static/lib/pdfjs/web/viewer.html?file=/web/content/#{widget.activeAttachment.id}?model%3D#{model}" />
-                    <iframe t-if="(widget.activeAttachment.type || '').indexOf('text') !== -1" class="mt32 o_viewer_text" t-attf-src="/web/content/#{widget.activeAttachment.id}?model%3D#{model}" />
-                    <iframe t-if="widget.activeAttachment.type == 'youtu'" class="mt32 o_viewer_text"  allow="autoplay; encrypted-media" width="560" height="315" t-attf-src="https://www.youtube.com/embed/#{widget.activeAttachment.youtube}"/>
-                    <video t-if="widget.activeAttachment.type == 'video'" class="o_viewer_video" controls="controls">
+                    <img t-if="widget.activeAttachment.fileType === 'image'" class="o_viewer_img" t-attf-src="/web/image/#{widget.activeAttachment.id}?unique=1&amp;signature=#{widget.activeAttachment.checksum}&amp;model=#{model}" alt="Viewer"/>
+                    <iframe t-if="widget.activeAttachment.fileType == 'application/pdf'" class="mt32 o_viewer_pdf"  t-attf-src="/web/static/lib/pdfjs/web/viewer.html?file=/web/content/#{widget.activeAttachment.id}?model%3D#{model}" />
+                    <iframe t-if="(widget.activeAttachment.fileType || '').indexOf('text') !== -1" class="mt32 o_viewer_text" t-attf-src="/web/content/#{widget.activeAttachment.id}?model%3D#{model}" />
+                    <iframe t-if="widget.activeAttachment.fileType == 'youtu'" class="mt32 o_viewer_text"  allow="autoplay; encrypted-media" width="560" height="315" t-attf-src="https://www.youtube.com/embed/#{widget.activeAttachment.youtube}"/>
+                    <video t-if="widget.activeAttachment.fileType == 'video'" class="o_viewer_video" controls="controls">
                         <source t-attf-src="/web/image/#{widget.activeAttachment.id}?model=#{model}" t-att-data-type="widget.activeAttachment.mimetype"/>
                     </video>
                 </div>
             </div>
-            <div t-if="widget.activeAttachment.type == 'image'" class="o_viewer_toolbar btn-toolbar" role="toolbar">
+            <div t-if="widget.activeAttachment.fileType == 'image'" class="o_viewer_toolbar btn-toolbar" role="toolbar">
                 <div class="btn-group ml0" role="group">
                     <a role="button" href="#" class="o_viewer_toolbar_btn btn o_zoom_in" data-toggle="tooltip" title="Zoom In"><i class="fa fa-fw fa-plus" role="img" aria-label="Zoom In"/></a>
                     <a role="button" href="#" class="o_viewer_toolbar_btn btn o_zoom_reset disabled" data-toggle="tooltip" title="Reset Zoom"><i class="fa fa-fw fa-search" role="img" aria-label="Reset Zoom"/></a>
diff --git a/addons/mail/static/tests/document_viewer_tests.js b/addons/mail/static/tests/document_viewer_tests.js
index 87fa2dbed94..b7ba9763386 100644
--- a/addons/mail/static/tests/document_viewer_tests.js
+++ b/addons/mail/static/tests/document_viewer_tests.js
@@ -206,5 +206,24 @@ QUnit.module('DocumentViewer', {
 
         assert.ok(viewer.isDestroyed(), 'viewer should be destroyed');
     });
+
+    QUnit.test('fileType and integrity test', function (assert) {
+        assert.expect(3);
+
+        var viewer = createViewer({
+            attachmentID: 2,
+            attachments: this.attachments,
+        });
+
+        assert.strictEqual(this.attachments[1].type, 'url',
+            "the type should be url");
+        assert.strictEqual(this.attachments[1].fileType, 'youtu',
+            "there should be a fileType 'youtu'");
+        assert.strictEqual(this.attachments[1].youtube, 'FYqW0Gdwbzk',
+            "there should be a youtube token");
+
+        viewer.destroy();
+    });
+
 });
 });