diff --git a/devito/finite_differences/differentiable.py b/devito/finite_differences/differentiable.py
index c6adfa50d4..64d850f317 100644
--- a/devito/finite_differences/differentiable.py
+++ b/devito/finite_differences/differentiable.py
@@ -745,7 +745,7 @@ def value(self, idx):
         except TypeError:
             # E.g., `idx` is a tuple
             v = self._npweights[idx]
-        if v.is_Number:
+        if v.is_Number or v.is_Indexed:
             return sympy.sympify(v)
         else:
             return self[idx]