diff --git a/wlauto/common/android/workload.py b/wlauto/common/android/workload.py
index ca4f3ea2..9483eafd 100644
--- a/wlauto/common/android/workload.py
+++ b/wlauto/common/android/workload.py
@@ -35,6 +35,7 @@ import wlauto.common.android.resources
 
 DELAY = 5
 
+
 # Due to the way `super` works you have to call it at every level but WA executes some
 # methods conditionally and so has to do them directly via the class, this breaks super
 # and causes it to run things mutiple times ect. As a work around for this untill workloads
@@ -221,7 +222,7 @@ class ApkWorkload(Workload):
             self.check_apk_version()
 
         if self.launch_main:
-            self.launch_package() # launch default activity without intent data
+            self.launch_package()  # launch default activity without intent data
         self.device.execute('am kill-all')  # kill all *background* activities
         self.device.clear_logcat()
 
diff --git a/wlauto/core/extension.py b/wlauto/core/extension.py
index 6611aa46..3340ff37 100644
--- a/wlauto/core/extension.py
+++ b/wlauto/core/extension.py
@@ -224,18 +224,11 @@ class Param(object):
         else:
             new_value = current_value + [value]
             setattr(obj, self.name, new_value)
-
-    def validate(self, obj):
-        value = getattr(obj, self.name, None)
         if value is not None:
             if self.allowed_values:
                 self._validate_allowed_values(obj, value)
             if self.constraint:
                 self._validate_constraint(obj, value)
-        else:
-            if self.mandatory:
-                msg = 'No value specified for mandatory parameter {} in {}.'
-                raise ConfigError(msg.format(self.name, obj.name))
 
     def get_type_name(self):
         typename = str(self.kind)
@@ -567,7 +560,9 @@ class Extension(object):
         if self.name is None:
             raise ValidationError('Name not set for {}'.format(self._classname))
         for param in self.parameters:
-            param.validate(self)
+            if param.mandatory and getattr(self, param.name, None) is None:
+                msg = 'No value specified for mandatory parameter {} in {}.'
+                raise ConfigError(msg.format(param.name, self.name))
 
     def initialize(self, context):
         pass
diff --git a/wlauto/utils/power.py b/wlauto/utils/power.py
index f50a6362..070714cf 100755
--- a/wlauto/utils/power.py
+++ b/wlauto/utils/power.py
@@ -682,7 +682,8 @@ def main():
     # pylint: disable=unbalanced-tuple-unpacking
     logging.basicConfig(level=logging.INFO)
     args = parse_arguments()
-    parallel_report, powerstate_report = report_power_stats(
+
+    reports = report_power_stats(
         trace_file=args.infile,
         idle_state_names=args.idle_state_names,
         core_names=args.core_names,
@@ -696,6 +697,10 @@ def main():
         max_freq_list=args.max_freq_list,
         start_marker_handling=args.start_marker_handling,
     )
+
+    parallel_report = reports.pop(0)
+    powerstate_report = reports.pop(0)
+
     parallel_report.write(os.path.join(args.output_directory, 'parallel.csv'))
     powerstate_report.write(os.path.join(args.output_directory, 'cpustate.csv'))