diff --git a/GPy/kern/_src/static.py b/GPy/kern/_src/static.py
index b32077e9..e7bee6c2 100644
--- a/GPy/kern/_src/static.py
+++ b/GPy/kern/_src/static.py
@@ -25,6 +25,8 @@ class Static(Kern):
         return np.zeros(X.shape)
 
     def gradients_XX(self, dL_dK, X, X2):
+        if X2 is None:
+            X2 = X
         return np.zeros((X.shape[0], X2.shape[0], X.shape[1]), dtype=np.float64)
     def gradients_XX_diag(self, dL_dKdiag, X):
         return np.zeros(X.shape)