diff --git a/ClusterController/Job.py b/ClusterController/Job.py
index 7b16064..fa69d70 100644
--- a/ClusterController/Job.py
+++ b/ClusterController/Job.py
@@ -27,7 +27,9 @@ class JobId:
 		A single integer is no longer enough to identify a job because all elements in a job array
 		share the same sge job identifier. To uniquely define a job array element, we also use the task id.
 	"""
+	MAX_NUM_JOBS_IN_ARRAY = 1000000
 	def __init__( self, iJobId, iJobArrayElementId = None):
+		assert iJobArrayElementId <= self.MAX_NUM_JOBS_IN_ARRAY
 		self.m_iJobId = iJobId
 		self.m_iJobArrayElementId = iJobArrayElementId # None if this identifier does not refer to a job array element
 		
@@ -35,7 +37,10 @@ class JobId:
 		"""
 			required to use a JobId as a dict hash key
 		"""
-		return self.m_iJobId # very simple hashing that conflicts only for job array elements
+		hash = self.m_iJobId * self.MAX_NUM_JOBS_IN_ARRAY
+		if self.m_iJobArrayElementId is not None:
+			hash += self.m_iJobArrayElementId
+		return hash
 	
 	def __eq__( self, other ):
 		"""