diff --git a/content/tutorials/security/sandboxed-iframes/en/index.html b/content/tutorials/security/sandboxed-iframes/en/index.html
index 95ee76da5..8b6aa8002 100644
--- a/content/tutorials/security/sandboxed-iframes/en/index.html
+++ b/content/tutorials/security/sandboxed-iframes/en/index.html
@@ -240,7 +240,7 @@ <h3 id="safely-sandboxing-eval">Safely sandboxing <code>eval()</code></h3>
        } catch (e) {
          result = 'eval() threw an exception.';
        }
-       mainWindow.postMessage(result, event.origin);
+       mainWindow.postMessage(result, e.origin);
      });
    &lt;/script&gt;
  &lt;/head&gt;
diff --git a/content/tutorials/security/sandboxed-iframes/en/index.markdown b/content/tutorials/security/sandboxed-iframes/en/index.markdown
index c5372dbf3..3b3d2f90f 100644
--- a/content/tutorials/security/sandboxed-iframes/en/index.markdown
+++ b/content/tutorials/security/sandboxed-iframes/en/index.markdown
@@ -218,7 +218,7 @@ inside out, starting with the frame's contents:
            } catch (e) {
              result = 'eval() threw an exception.';
            }
-           mainWindow.postMessage(result, event.origin);
+           mainWindow.postMessage(result, e.origin);
          });
        </script>
      </head>