diff --git a/lib/agenda.js b/lib/agenda.js
index 0f605f832..162ced564 100644
--- a/lib/agenda.js
+++ b/lib/agenda.js
@@ -675,11 +675,13 @@ function processJobs(extraJob) {
     if (err && !job) throw(err)
     var name = job.attrs.name;
 
+    if (self._runningJobs.indexOf(job) == -1) throw("callback already called - job " + name + " already marked complete");
+
     self._runningJobs.splice(self._runningJobs.indexOf(job), 1);
-    definitions[name].running--;
+    if (definitions[name].running > 0) definitions[name].running--;
 
     self._lockedJobs.splice(self._lockedJobs.indexOf(job), 1);
-    definitions[name].locked--;
+    if (definitions[name].locked > 0) definitions[name].locked--;
 
     jobProcessing();
   }