diff --git a/format/html.go b/format/html.go
index 7ea8b59..a3dee36 100644
--- a/format/html.go
+++ b/format/html.go
@@ -47,7 +47,7 @@ func htmlElement(el element.Element) string {
 	case element.ListItem:
 		return fmt.Sprintf("<li>%s</li>\n", HTMLFragment(v...))
 	case element.CodeBlock:
-		return fmt.Sprintf("<pre><code>%s</code></pre>", v.Text())
+		return fmt.Sprintf("<pre><code>%s</code></pre>", html.EscapeString(v.Text()))
 	case element.Paragraph:
 		return fmt.Sprintf("<p>%s</p>\n", HTMLFragment(v.Elements...))
 	case element.Strong:
diff --git a/format/html_test.go b/format/html_test.go
index 7b6517e..12e3ac4 100644
--- a/format/html_test.go
+++ b/format/html_test.go
@@ -141,12 +141,12 @@ func TestHTMLFragment(t *testing.T) {
 				element.WhiteSpace(" "),
 				element.Word("text"),
 				element.WhiteSpace("\n"),
-				element.Word("with"),
+				element.Word("<p>with</p>"),
 				element.WhiteSpace("\t"),
 				element.Word("formatting"),
 			},
 			exp: `<pre><code>some text
-with	formatting</code></pre>`,
+&lt;p&gt;with&lt;/p&gt;	formatting</code></pre>`,
 		},
 		{
 			name:  "subtitle",