diff --git a/plugins/mattermost/index.js b/plugins/mattermost/index.js
index 66e0343ef475b931253f63df2f1d9922dd3f26d0..131c1226cc28bbcec986f705e01a8d8e85a741a6 100644
--- a/plugins/mattermost/index.js
+++ b/plugins/mattermost/index.js
@@ -60,12 +60,15 @@ exports.initWebApp = function(options) {
   var image = function(alt, url, width, height) {
     var size = '';
     if (width != undefined) {
-      size = ' =' + width + 'x';
-      if (height != undefined) {
-        size += height;
-      }
+      size += ' width="' + width + 'px"';
+    }
+    if (height != undefined) {
+      size += ' height="' + height + 'px"';
+    }
+    else {
+      size += ' height="32px"';
     }
-    return '![' + alt + '](' + url + size + ')';
+    return '<img' + size + ' src="' + url + '" />';
   };
 
   var getHook = function(check) {