--- a/taskcluster/taskgraph/decision.py
+++ b/taskcluster/taskgraph/decision.py
@@ -183,17 +183,19 @@ def taskgraph_decision(options, paramete
 
      * processing decision task command-line options into parameters
      * running task-graph generation exactly the same way the other `mach
        taskgraph` commands do
      * generating a set of artifacts to memorialize the graph
      * calling TaskCluster APIs to create the graph
     """
 
-    parameters = parameters or (lambda config: get_decision_parameters(config, options))
+    parameters = parameters or (
+        lambda graph_config: get_decision_parameters(graph_config, options)
+    )
 
     # create a TaskGraphGenerator instance
     tgg = TaskGraphGenerator(
         root_dir=options.get('root'),
         parameters=parameters)
 
     # write out the parameters used to generate this graph
     write_artifact('parameters.yml', dict(**tgg.parameters))
@@ -218,23 +220,23 @@ def taskgraph_decision(options, paramete
     # and the map of labels to taskids
     write_artifact('task-graph.json', tgg.morphed_task_graph.to_json())
     write_artifact('label-to-taskid.json', tgg.label_to_taskid)
 
     # actually create the graph
     create_tasks(tgg.graph_config, tgg.morphed_task_graph, tgg.label_to_taskid, tgg.parameters)
 
 
-def get_decision_parameters(config, options):
+def get_decision_parameters(graph_config, options):
     """
     Load parameters from the command-line options for 'taskgraph decision'.
     This also applies per-project parameters, based on the given project.
 
     """
-    product_dir = config['product-dir']
+    product_dir = graph_config['product-dir']
 
     parameters = {n: options[n] for n in [
         'base_repository',
         'head_repository',
         'head_rev',
         'head_ref',
         'project',
         'pushlog_id',
@@ -311,17 +313,17 @@ def get_decision_parameters(config, opti
 
     # ..but can be overridden by the commit message: if it contains the special
     # string "DONTBUILD" and this is an on-push decision task, then use the
     # special 'nothing' target task method.
     if 'DONTBUILD' in commit_message and options['tasks_for'] == 'hg-push':
         parameters['target_tasks_method'] = 'nothing'
 
     if options.get('include_push_tasks'):
-        get_existing_tasks(options.get('rebuild_kinds', []), parameters, config)
+        get_existing_tasks(options.get('rebuild_kinds', []), parameters, graph_config)
 
     # If the target method is nightly, we should build partials. This means
     # knowing what has been released previously.
     # An empty release_history is fine, it just means no partials will be built
     parameters.setdefault('release_history', dict())
     if 'nightly' in parameters.get('target_tasks_method', ''):
         parameters['release_history'] = populate_release_history('Firefox', project)