diff --git a/GPy/models/gp_regression.py b/GPy/models/gp_regression.py
index 7266ae92..157c0dc8 100644
--- a/GPy/models/gp_regression.py
+++ b/GPy/models/gp_regression.py
@@ -26,12 +26,12 @@ class GPRegression(GP):
 
     """
 
-    def __init__(self, X, Y, kernel=None, Y_metadata=None, normalizer=None, noise_var=1.):
+    def __init__(self, X, Y, kernel=None, Y_metadata=None, normalizer=None, noise_var=1., mean_function=None):
 
         if kernel is None:
             kernel = kern.RBF(X.shape[1])
-	
+
         likelihood = likelihoods.Gaussian(variance=noise_var)
 
-        super(GPRegression, self).__init__(X, Y, kernel, likelihood, name='GP regression', Y_metadata=Y_metadata, normalizer=normalizer)
+        super(GPRegression, self).__init__(X, Y, kernel, likelihood, name='GP regression', Y_metadata=Y_metadata, normalizer=normalizer, mean_function=mean_function)