diff --git a/lib/OptiPng.js b/lib/OptiPng.js
index e09dd00..71cc45c 100644
--- a/lib/OptiPng.js
+++ b/lib/OptiPng.js
@@ -105,13 +105,15 @@ OptiPng.prototype.end = function end(chunk) {
         }.bind(this));
         this.readStream.once('end', function onReadStreamEnd() {
             this.push(null); // null closes the stream
-            fs.unlink(this.tempFile, function onUnlink(err){
-                // not emitting this error since stream is done
-                if (err) {
-                    console.error(err.stack);
-                }
-            });
-            this.tempFile = null;
+            if (this.tempFile) {
+                fs.unlink(this.tempFile, function onUnlink(err){
+                    // not emitting this error since stream is done
+                    if (err) {
+                        console.error(err.stack);
+                    }
+                });
+                this.tempFile = null;
+            }
         }.bind(this));
     }.bind(this);
 };