diff --git a/src/numpydantic/interface/hdf5.py b/src/numpydantic/interface/hdf5.py
index 0dac4c6..9250353 100644
--- a/src/numpydantic/interface/hdf5.py
+++ b/src/numpydantic/interface/hdf5.py
@@ -112,9 +112,13 @@ class H5Proxy:
     ):
         with h5py.File(self.file, "r+", locking=True) as h5f:
             obj = h5f.get(self.path)
-            if self.field is not None:
-                obj = obj.fields(self.field)
-            obj[key] = value
+            if self.field is None:
+                obj[key] = value
+            else:
+                if isinstance(key, tuple):
+                    obj[*key, self.field] = value
+                else:
+                    obj[key, self.field] = value
 
     def open(self, mode: str = "r") -> "h5py.Dataset":
         """
diff --git a/tests/test_interface/test_hdf5.py b/tests/test_interface/test_hdf5.py
index cdb255a..23d26a3 100644
--- a/tests/test_interface/test_hdf5.py
+++ b/tests/test_interface/test_hdf5.py
@@ -150,3 +150,10 @@ def test_compound_dtype(tmp_path):
     assert instance.array.dtype == np.dtype("int64")
     assert instance.array.shape == (10, 20)
     assert instance.array[0, 0] == 0
+
+    # set values too
+    instance.array[0, :] = 1
+    assert all(instance.array[0, :] == 1)
+    assert all(instance.array[1, :] == 0)
+    instance.array[1] = 2
+    assert all(instance.array[1] == 2)