diff --git a/pymc3/distributions/multivariate.py b/pymc3/distributions/multivariate.py
index e89bebe1f49..4760fe7e38f 100644
--- a/pymc3/distributions/multivariate.py
+++ b/pymc3/distributions/multivariate.py
@@ -179,12 +179,13 @@ class Dirichlet(MultivariateContinuous):
     as a parent of Multinomial and Categorical nevertheless.
     """
 
-    def __init__(self, a, transform=transforms.stick_breaking, ndim=None, size=None, dtype=None, *args, **kwargs):
+    def __init__(self, a, transform=transforms.stick_breaking, ndim=None,
+                 size=None, dtype=None, *args, **kwargs):
         self.a = tt.as_tensor_variable(a)
         self.mean = self.a / tt.sum(self.a)
         self.mode = tt.switch(tt.all(self.a > 1),
-                             (self.a - 1) / tt.sum(self.a - 1),
-                             np.nan)
+                              (self.a - 1) / tt.sum(self.a - 1),
+                              np.nan)
 
         self.dist_params = (self.a,)