diff --git a/Dockstore.cwl b/Dockstore.cwl
index 1d4acbb..3557928 100644
--- a/Dockstore.cwl
+++ b/Dockstore.cwl
@@ -24,7 +24,7 @@ dct:creator:
 
 requirements:
   - class: DockerRequirement
-    dockerPull: "quay.io/ucsc_cgl/dockstore-tool-runner:1.0.20"
+    dockerPull: "quay.io/ucsc_cgl/dockstore-tool-runner:1.0.21"
 
 hints:
   - class: ResourceRequirement
diff --git a/DockstoreRunner.py b/DockstoreRunner.py
index c93b763..78fe602 100644
--- a/DockstoreRunner.py
+++ b/DockstoreRunner.py
@@ -474,7 +474,7 @@ def run(self):
    "analysis_type" : "%s",
    "bundle_uuid" : "%s",
    "workflow_params" : {
-''' % (str(utc_datetime.isoformat("T")), self.parent_uuids.split(","), self.dockstore_url, self.workflow_name, self.workflow_version, self.workflow_type, self.bundle_uuid)
+''' % (str(utc_datetime.isoformat("T")), json.dumps(self.parent_uuids.split(",")), self.dockstore_url, self.workflow_name, self.workflow_version, self.workflow_type, self.bundle_uuid)
         i=0
         (params_map, file_input_map) = self.map_params(transformed_json_path)
         params_map_keys = params_map.keys()