diff --git a/GPy/core/transformations.py b/GPy/core/transformations.py
index 41d0eaf9..ff821851 100644
--- a/GPy/core/transformations.py
+++ b/GPy/core/transformations.py
@@ -48,6 +48,7 @@ class logexp_clipped(transformation):
         return np.log(np.exp(f) - 1.)
     def gradfactor(self, f):
         ef = np.exp(f)
+        gf = (ef - 1.) / ef
         return np.where(f < 1e-6, 0, gf)
     def initialize(self,f):
         if np.any(f<0.):