diff --git a/src/nupic/swarming/exp_generator/experiment_generator.py b/src/nupic/swarming/exp_generator/experiment_generator.py
index 0c9adf0c05..f0eb242540 100755
--- a/src/nupic/swarming/exp_generator/experiment_generator.py
+++ b/src/nupic/swarming/exp_generator/experiment_generator.py
@@ -1858,7 +1858,7 @@ def _generateMetricSpecs(options):
 
 def _generateExtraMetricSpecs(options):
   """Generates the non-default metrics specified by the expGenerator params """
-  global _metricSpecSchema
+  _metricSpecSchema = {'properties': {}}
 
   results = []
   for metric in options['metrics']: