diff --git a/hugr-py/src/hugr/serialization/ops.py b/hugr-py/src/hugr/serialization/ops.py
index 39d2a5676..d76b13e84 100644
--- a/hugr-py/src/hugr/serialization/ops.py
+++ b/hugr-py/src/hugr/serialization/ops.py
@@ -2,7 +2,7 @@
 import inspect
 import sys
 from abc import ABC, abstractmethod
-from typing import Any, Literal
+from typing import Any, Literal, TYPE_CHECKING
 
 from pydantic import Field, RootModel, ConfigDict
 
@@ -22,6 +22,9 @@
 )
 from hugr.utils import deser_it
 
+if TYPE_CHECKING:
+    from hugr.serialization.serial_hugr import SerialHugr
+
 NodeID = int
 
 
@@ -101,10 +104,12 @@ class FunctionValue(BaseValue):
     """A higher-order function value."""
 
     v: Literal["Function"] = Field(default="Function", title="ValueTag")
-    hugr: Any  # TODO
+    hugr: SerialHugr
 
     def deserialize(self) -> _val.Value:
-        return _val.Function(self.hugr)
+        from hugr._hugr import Hugr
+
+        return _val.Function(Hugr.from_serial(self.hugr))
 
 
 class TupleValue(BaseValue):
@@ -604,7 +609,9 @@ class OpDef(ConfiguredBaseModel, populate_by_name=True):
     + tys_classes
 )
 
-tys_model_rebuild(dict(classes))
+# needed to avoid circular imports
+from hugr import _ops  # noqa: E402
+from hugr import _val  # noqa: E402
+from hugr.serialization.serial_hugr import SerialHugr  # noqa: E402
 
-from hugr import _ops  # noqa: E402  # needed to avoid circular imports
-from hugr import _val  # noqa: E402  # needed to avoid circular imports
+tys_model_rebuild(dict(classes))
diff --git a/hugr-py/src/hugr/serialization/serial_hugr.py b/hugr-py/src/hugr/serialization/serial_hugr.py
index 49bfbd2f7..1dc60176b 100644
--- a/hugr-py/src/hugr/serialization/serial_hugr.py
+++ b/hugr-py/src/hugr/serialization/serial_hugr.py
@@ -1,11 +1,12 @@
+from __future__ import annotations
 from typing import Any, Literal
 
 from pydantic import Field, ConfigDict
 
-from .ops import NodeID, OpType, classes as ops_classes
 from .tys import model_rebuild, ConfiguredBaseModel
 import hugr
 
+NodeID = int
 Port = tuple[NodeID, int | None]  # (node, offset)
 Edge = tuple[Port, Port]
 
@@ -48,3 +49,6 @@ def _pydantic_rebuild(cls, config: ConfigDict = ConfigDict(), **kwargs):
             "required": ["version", "nodes", "edges"],
         },
     )
+
+
+from .ops import OpType, classes as ops_classes  # noqa: E402 # needed to avoid circular import
diff --git a/hugr-py/tests/test_hugr_build.py b/hugr-py/tests/test_hugr_build.py
index 79dc24d0e..f37f283bd 100644
--- a/hugr-py/tests/test_hugr_build.py
+++ b/hugr-py/tests/test_hugr_build.py
@@ -128,12 +128,15 @@ def test_stable_indices():
     assert h._free_nodes == []
 
 
-def test_simple_id():
+def simple_id() -> Dfg:
     h = Dfg(tys.Qubit, tys.Qubit)
     a, b = h.inputs()
     h.set_outputs(a, b)
+    return h
 
-    _validate(h.hugr)
+
+def test_simple_id():
+    _validate(simple_id().hugr)
 
 
 def test_multiport():
@@ -266,3 +269,17 @@ def test_ancestral_sibling():
     nt = nested.add(Not(a))
 
     assert _ancestral_sibling(h.hugr, h.input_node, nt) == nested.parent_node
+
+
+@pytest.mark.parametrize(
+    "val",
+    [
+        val.Function(simple_id().hugr),
+        val.Sum(1, tys.Sum([[INT_T], [tys.Bool, INT_T]]), [IntVal(34)]),
+    ],
+)
+def test_vals(val: val.Value):
+    d = Dfg()
+    d.set_outputs(d.add_load_const(val))
+
+    _validate(d.hugr)