diff --git a/src/SourceMap.js b/src/SourceMap.js
index 27c1623..e5ce40b 100644
--- a/src/SourceMap.js
+++ b/src/SourceMap.js
@@ -4,7 +4,7 @@ let btoa = () => {
 	throw new Error('Unsupported environment: `window.btoa` or `Buffer` should be supported.');
 };
 if (typeof window !== 'undefined' && typeof window.btoa === 'function') {
-	btoa = window.btoa;
+	btoa = str => window.btoa(unescape(encodeURIComponent(str)));
 } else if (typeof Buffer === 'function') {
 	btoa = str => Buffer.from(str, 'utf-8').toString('base64');
 }