diff --git a/server/modules/rendering/html-security/renderer.js b/server/modules/rendering/html-security/renderer.js
index 956ae6c5..1ab73cbf 100644
--- a/server/modules/rendering/html-security/renderer.js
+++ b/server/modules/rendering/html-security/renderer.js
@@ -35,7 +35,9 @@ module.exports = {
       //Changes to keep interactive plantuml object tag
 
       //only allow specific attributes for plantuml object node
-      if (`${pumlImageFormat}` == 'svg') {
+      if (typeof pumlImageFormat !== 'undefined' &&
+          pumlImageFormat &&
+          pumlImageFormat  == 'svg') {
         allowedTags.push('object')
         allowedAttrs.push('data')
         allowedAttrs.push('type')
@@ -51,7 +53,12 @@ module.exports = {
         // insert the plantuml inside the object as text for search
         let isPumlNode=false
 
-        if (data.tagName === 'object') {
+        if (data.tagName === 'object' &&
+            typeof pumlServer !== 'undefined' && pumlServer &&
+            typeof pumlObjectStyle !== 'undefined' && pumlObjectStyle &&
+            typeof pumlObjectType !== 'undefined' && pumlObjectType &&
+            typeof pumlObjectClass !== 'undefined' && pumlObjectClass
+        ) {
           //console.log ("Found object node - validating")
           //remove node if it doesn't conform to plantuml structure
           if (!( 'data' in node.attributes
@@ -72,9 +79,9 @@ module.exports = {
           ) {
             //console.log ("Plantuml node found - setting atribute values")
             isPumlNode=true
-            node.setAttribute ('type', `${pumlObjectType}`)
-            node.setAttribute ('style', `${pumlObjectStyle}`)
-            node.setAttribute ('class', `${pumlObjectClass}`)
+            node.setAttribute ('type', pumlObjectType)
+            node.setAttribute ('style', pumlObjectStyle)
+            node.setAttribute ('class', pumlObjectClass)
             node.setAttribute ('alt', '')
           }
 
diff --git a/server/modules/rendering/markdown-plantuml/renderer.js b/server/modules/rendering/markdown-plantuml/renderer.js
index 8c12961f..428086e2 100644
--- a/server/modules/rendering/markdown-plantuml/renderer.js
+++ b/server/modules/rendering/markdown-plantuml/renderer.js
@@ -129,7 +129,7 @@ module.exports = {
           // alt is constructed from children. No point in populating it here.
           token.attrs = [ [ 'src' , `${server}/${imageFormat}/${zippedCode}` ],
                           [ 'alt' , '' ],
-                          ['class', `${pumlObjectClass}` ]
+                          ['class', pumlObjectClass ]
                         ]
           token.block = true
           token.children = altToken
@@ -145,9 +145,9 @@ module.exports = {
           token = state.push('uml_diagram_obj', 'object', 0)
           token.attrs = [ [ 'data' , `${server}/${imageFormat}/${zippedCode}`],
                           [ 'alt'  ,  '' ],
-                          [ 'class', `${pumlObjectClass}` ],
-                          [ 'style', `${pumlObjectStyle}` ],
-                          [ 'type',  `${pumlObjectType}`  ]
+                          [ 'class', pumlObjectClass ],
+                          [ 'style', pumlObjectStyle ],
+                          [ 'type',  pumlObjectType  ]
                         ]
           token.block = true
           token.children = altToken
@@ -164,7 +164,7 @@ module.exports = {
           // alt is constructed from children. No point in populating it here.
           token.attrs = [ [ 'src' , `${server}/${imageFormat}/${zippedCode}` ],
                           [ 'alt' , '' ],
-                          ['class', `${pumlObjectClass}`]
+                          ['class', pumlObjectClass]
                         ]
           token.block = true
           token.children = altToken