diff --git a/lib/less/source-map-output.js b/lib/less/source-map-output.js
index 9a090d4e4..b95d7c230 100644
--- a/lib/less/source-map-output.js
+++ b/lib/less/source-map-output.js
@@ -127,7 +127,7 @@
             if (this._writeSourceMap) {
                 this._writeSourceMap(sourceMapContent);
             } else {
-                sourceMapURL = "data:application/json," + encodeURIComponent(sourceMapContent);
+                sourceMapURL = "data:application/json;base64," + require('./encoder.js').encodeBase64(sourceMapContent);
             }
 
             if (sourceMapURL) {