diff --git a/sequence_processing_pipeline/Job.py b/sequence_processing_pipeline/Job.py
index 1c1a7593..b650543e 100644
--- a/sequence_processing_pipeline/Job.py
+++ b/sequence_processing_pipeline/Job.py
@@ -226,6 +226,9 @@ def wait_on_job_ids(self, job_ids, callback=None):
         # them before returning, optionally submitting callbacks for each
         # job-id.
 
+        # ensure all ids are strings to ensure proper working w/join().
+        job_ids = [str(x) for x in job_ids]
+
         def query_slurm(job_ids):
             # internal function query_slurm encapsulates the handling of
             # squeue.