diff --git a/README.md b/README.md
index 0c62d18..f6c671b 100644
--- a/README.md
+++ b/README.md
@@ -9,9 +9,11 @@
 - `ruamel.yaml`
 
 ### Installing Dependencies
-We recommend the use of `conda` to manage all dependencies. If you're not sure what `conda` is, make sure to read the [using-conda](conda documentation).
+We recommend the use of `conda` to manage all dependencies. If you're not sure what `conda` is, make sure to read about the [conda project](https://conda.io/docs/index.html).
 
-The easiest way to get you started with CTD conversion is to create a `conda` environment on which you'll install all dependencies. Using environments in `conda` allows you to have parallel, independent python environments, thus avoiding conflicts between libraries. If you haven't installed `conda`, check [conda-install](conda's installation guide).
+The easiest way to get you started with CTD conversion is to create a `conda` environment on which you'll install all dependencies.  Using environments in `conda` allows you to have parallel, independent python environments, thus avoiding conflicts between libraries. 
+
+If you haven't installed `conda`, check [conda-install](conda's installation guide). See [this guide](https://conda.io/docs/user-guide/tasks/manage-environments.html) if you need help creating a `conda` environment.
 
 Once you've installed `conda`, create an environment named `ctd-converter`, like so:
 
@@ -181,4 +183,4 @@
 [CTDopts]: https://github.com/genericworkflownodes/CTDopts
 [CTDSchema]: https://github.com/WorkflowConversion/CTDSchema
 [conda-install]: https://conda.io/docs/install/quick.html
-[using-conda]: https://conda.io/docs/using/envs.html
\ No newline at end of file
+[using-conda]: https://conda.io/docs/using/envs.html
diff --git a/galaxy/converter.py b/galaxy/converter.py
index 7f3e542..7dfd1cb 100755
--- a/galaxy/converter.py
+++ b/galaxy/converter.py
@@ -510,7 +510,7 @@
         rep_node.attrib["min"] = "0"
     # for the ITEMLISTs which have LISTITEM children we only
     # need one parameter as it is given as a string
-    if param.default is not None: 
+    if param.default is not None and param.default is not _Null:  
         rep_node.attrib["max"] = "1"
     rep_node.attrib["title"] = get_galaxy_parameter_name(param)