diff --git a/lib/parser-sync.js b/lib/parser-sync.js
index 8667b5f..54113af 100644
--- a/lib/parser-sync.js
+++ b/lib/parser-sync.js
@@ -52,9 +52,6 @@ module.exports = function(buffer, options) {
     error: handleError,
     metadata: handleMetaData,
     gamma: handleGamma,
-    finished: function() {
-      //todo make optional
-    },
     inflateData: handleInflateData,
     createData: createData
   });
diff --git a/lib/parser.js b/lib/parser.js
index 2eddfaf..2d49dc8 100644
--- a/lib/parser.js
+++ b/lib/parser.js
@@ -286,5 +286,7 @@ Parser.prototype._parseIEND = function(data) {
   this._hasIEND = true;
   this._handleChunkEnd();
 
-  this.finished();
+  if (this.finished) {
+    this.finished();
+  }
 };