TypeError: unhashable type: 'CommentedMap'

I converted a working draft-3 CWL file to a version 1.0 CWL file by changing the following.
1. `"cwlVersion": "draft-3",` -> `"cwlVersion": "v1.0",`
2. `"inputs"` -> `"in"` for all STEP inputs (but not workflow inputs)
3. `"outputs"` -> `"out"` for all STEP outputs (but not workflow outputs)
4. `"source"` -> `"outputSource"` for all workflow outputs (but not step inputs)

(My file doesn't have a field 'description')

I'm getting the following error when running the latest master of cwltool.
```
Traceback (most recent call last):
File "/home/ec2-user/venv/cwl/local/lib/python2.7/site-packages/cwltool/main.py", line 492, in main
makeTool, make_tool_kwds)
File "/home/ec2-user/venv/cwl/local/lib/python2.7/site-packages/cwltool/load_tool.py", line 341, in make_tool
tool = makeTool(processobj, **kwargs)
File "/home/ec2-user/venv/cwl/local/lib/python2.7/site-packages/cwltool/workflow.py", line 44, in defaultMakeTool
return Workflow(toolpath_object, **kwargs)
File "/home/ec2-user/venv/cwl/local/lib/python2.7/site-packages/cwltool/workflow.py", line 432, in __init__
self.steps.append(WorkflowStep(step, n, **kwargs))
File "/home/ec2-user/venv/cwl/local/lib/python2.7/site-packages/cwltool/workflow.py", line 550, in __init__
+ "\n" + SourceLine(self.embedded_tool.tool, "outputs").makeError(
File "/home/ec2-user/venv/cwl/local/lib/python2.7/site-packages/cwltool/process.py", line 171, in shortname
d = urllib.parse.urlparse(inputid)
File "/usr/lib64/python2.7/urlparse.py", line 143, in urlparse
tuple = urlsplit(url, scheme, allow_fragments)
File "/usr/lib64/python2.7/urlparse.py", line 176, in urlsplit
cached = _parse_cache.get(key, None)
TypeError: unhashable type: 'CommentedMap'
```
I'm not sure if I can get what exactly is wrong with this CWL file. Some help would be appreciated.
Thanks.