diff --git a/lib/index.js b/lib/index.js
index <HASH>..<HASH> 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -38,12 +38,15 @@ function fork(options, callback) {
   if (!promise) {
     defer = Q.defer();
     cache[key] = promise = defer.promise;
+    promise._firstCall = true;
   }
 
   promise.done(function(result) {
-    callback(null, result[0], result[1]);
+    callback(null, result[0], result[1], promise._firstCall);
+    promise._firstCall = false;
   }, function(err) {
-    callback(err);
+    callback(err, undefined, undefined, promise._firstCall);
+    promise._firstCall = false;
   });
 
   if (!defer) {
feat: mark the callback for the first execution