diff --git a/diceware/random_sources.py b/diceware/random_sources.py
index f965f2af482444ec4e888bfee587280f44b02c5f..2e3c8fd52d165f484867bd5b1603bd9f5e0336a4 100644
--- a/diceware/random_sources.py
+++ b/diceware/random_sources.py
@@ -151,7 +151,8 @@ class RealDiceRandomSource(object):
         result = 0
         for i in range(num_rolls, 0, -1):
             rolled = None
-            while rolled not in [str(x) for x in range(1, self.dice_sides + 1)]:
+            while rolled not in [
+                    str(x) for x in range(1, self.dice_sides + 1)]:
                 rolled = input_func(
                     "What number shows dice number %s? " % (num_rolls - i + 1))
             result += ((self.dice_sides ** (i - 1)) * (int(rolled) - 1))