diff --git a/src/Clone.js b/src/Clone.js
index 018e6dc..553e21b 100644
--- a/src/Clone.js
+++ b/src/Clone.js
@@ -230,9 +230,17 @@ export class DocumentCloner {
         }
 
         if (node instanceof HTMLStyleElement && node.sheet && node.sheet.cssRules) {
-            const css = [].slice
-                .call(node.sheet.cssRules, 0)
-                .reduce((css, rule) => css + rule.cssText, '');
+            const css = [].slice.call(node.sheet.cssRules, 0).reduce((css, rule) => {
+                try {
+                    if (rule && rule.cssText) {
+                        return css + rule.cssText;
+                    }
+                    return css;
+                } catch (err) {
+                    this.logger.log('Unable to access cssText property', rule.name);
+                    return css;
+                }
+            }, '');
             const style = node.cloneNode(false);
             style.textContent = css;
             return style;