diff -r 0d948a46c59a Lib/statistics.py
--- a/Lib/statistics.py	Sun Oct 02 21:59:44 2016 +0300
+++ b/Lib/statistics.py	Mon Oct 03 20:07:45 2016 +0900
@@ -561,10 +561,11 @@ def geometric_mean(data):
     errmsg = 'geometric mean does not support negative values'
     n = len(data)
     if n < 1:
-        raise StatisticsError('geometric_mean requires at least one data point')
+        raise StatisticsError(
+            'geometric_mean requires at least one data point')
     elif n == 1:
         x = data[0]
-        if isinstance(g, (numbers.Real, Decimal)):
+        if isinstance(x, (numbers.Real, Decimal)):
             if x < 0:
                 raise StatisticsError(errmsg)
             return x