diff --git a/GPy/core/parameterized.py b/GPy/core/parameterized.py
index 45aa70d5..4e556640 100644
--- a/GPy/core/parameterized.py
+++ b/GPy/core/parameterized.py
@@ -195,7 +195,7 @@ class Parameterized(object):
 
     def constrain_negative(self, regexp):
         """ Set negative constraints. """
-        self.constrain(regexp, transformations.Negative_logexp())
+        self.constrain(regexp, transformations.NegativeLogexp())
 
     def constrain_positive(self, regexp):
         """ Set positive constraints. """
diff --git a/GPy/core/transformations.py b/GPy/core/transformations.py
index 17e50507..0524dfe3 100644
--- a/GPy/core/transformations.py
+++ b/GPy/core/transformations.py
@@ -43,7 +43,7 @@ class Logexp(Transformation):
     def __str__(self):
         return '(+ve)'
 
-class Negative_logexp(Transformation):
+class NegativeLogexp(Transformation):
     domain = NEGATIVE
     def f(self, x):
         return -Logexp.f(x)  # np.log(1. + np.exp(x))