diff --git a/src/re/multi_grid/grid_impl.py b/src/re/multi_grid/grid_impl.py
index 7bd60d765782406083ecea5acc586746c2bb0ade..37b9b300bca924edb7ccd2eabc723f3cd5306e31 100644
--- a/src/re/multi_grid/grid_impl.py
+++ b/src/re/multi_grid/grid_impl.py
@@ -116,7 +116,7 @@ class HEALPixGrid(Grid):
 
         assert shape0 is None or isinstance(shape0, (int, tuple, np.ndarray))
         if shape0 is not None:
-            shape0 = np.asarray(shape0).flatten()
+            shape0 = np.asarray(shape0).ravel()
             assert (
                 shape0.size == 1
             ), "shape0 must be a scalar or a single-element array/tuple"