diff --git a/CHANGELOG.md b/CHANGELOG.md
index dd8a7e49..3f61ee30 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -17,6 +17,9 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ### Changed
 * [Breaking] Renamed `unsafeCss` to `unsafeCSS` for consistency with lit-html's `unsafeHTML`
 
+### Fixed
+* Adds a check to ensure `CSSStyleSheet` is constructable ([#525](https://github.com/Polymer/lit-element/issues/525)).
+
 ## [2.0.0-rc.5] - 2019-01-24
 ### Fixed
 * Fixed a bug causing duplicate styles when an array was returned from `static get styles` ([#480](https://github.com/Polymer/lit-element/issues/480)).
diff --git a/src/lib/css-tag.ts b/src/lib/css-tag.ts
index eb36feaf..8b38ab42 100644
--- a/src/lib/css-tag.ts
+++ b/src/lib/css-tag.ts
@@ -10,7 +10,7 @@ found at http://polymer.github.io/PATENTS.txt
 */
 
 export const supportsAdoptingStyleSheets =
-    ('adoptedStyleSheets' in Document.prototype);
+    ('adoptedStyleSheets' in Document.prototype) && ('replace' in CSSStyleSheet.prototype);
 
 const constructionToken = Symbol();