diff --git a/lib/CachedSource.js b/lib/CachedSource.js
index df02706..08ca510 100644
--- a/lib/CachedSource.js
+++ b/lib/CachedSource.js
@@ -31,7 +31,7 @@ class CachedSource extends Source {
 	size() {
 		if(typeof this._cachedSize !== "undefined") return this._cachedSize;
 		if(typeof this._cachedSource !== "undefined") {
-			if(Buffer.from.length === 1) return new Buffer(this.source()).length;
+			if(Buffer.from.length === 1) return new Buffer(this._cachedSource).length;
 			return this._cachedSize = Buffer.byteLength(this._cachedSource);
 		}
 		return this._cachedSize = this._source.size();