diff --git a/core/vendor/core.js b/core/vendor/core.js
index 8cdb203aacde9cf0843c5192fa1997e6529f3b01..bda270892ad91b678e97d891eb14595366cf4cb4 100644
--- a/core/vendor/core.js
+++ b/core/vendor/core.js
@@ -5551,6 +5551,9 @@ dav.Client.prototype = {
             '  <d:prop>\n';
 
         for(var ii in properties) {
+            if (!properties.hasOwnProperty(ii)) {
+                continue;
+            }
 
             var property = this.parseClarkNotation(properties[ii]);
             if (this.xmlNamespaces[property.namespace]) {
@@ -5596,6 +5599,10 @@ dav.Client.prototype = {
             '   <d:prop>\n';
 
         for(var ii in properties) {
+            if (!properties.hasOwnProperty(ii)) {
+                continue;
+            }
+
             var property = this.parseClarkNotation(ii);
             var propName;
             var propValue = properties[ii];