diff --git a/GPy/kern/_src/stationary.py b/GPy/kern/_src/stationary.py
index ef8900f9..055a945e 100644
--- a/GPy/kern/_src/stationary.py
+++ b/GPy/kern/_src/stationary.py
@@ -168,11 +168,14 @@ class Stationary(Kern):
 
         #the lower memory way with a loop
         tmp = invdist*dL_dr
-        if X2 is None:
-            tmp *= 2.
-            X2 = X
         ret = np.empty(X.shape, dtype=np.float64)
-        [np.einsum('ij,ij->i', tmp, X[:,q][:,None]-X2[:,q][None,:], out=ret[:,q]) for q in xrange(self.input_dim)]
+        if X2 is None:
+            [np.einsum('ij,ij->i', tmp, X[:,q][:,None]-X[:,q][None,:], out=ret[:,q]) for q in xrange(self.input_dim)]
+            ret2 = np.empty(X.shape, dtype=np.float64)
+            [np.einsum('ij,ji->j', tmp, X[:,q][:,None]-X[:,q][None,:], out=ret2[:,q]) for q in xrange(self.input_dim)]
+            ret += ret2
+        else:
+            [np.einsum('ij,ij->i', tmp, X[:,q][:,None]-X2[:,q][None,:], out=ret[:,q]) for q in xrange(self.input_dim)]
         ret /= self.lengthscale**2
         return ret