diff --git a/pyzx/generate.py b/pyzx/generate.py
index 54b917ff..349d4a4a 100644
--- a/pyzx/generate.py
+++ b/pyzx/generate.py
@@ -99,6 +99,7 @@ def spider(
         set_z_box_label(g, v_in, phase)
         v_out = v_in
     else:
+        assert isinstance(phase, (int, Fraction))
         v_in = g.add_vertex(typ, (inputs-1)/2, 1, phase)
         v_out = v_in
     inp = []
diff --git a/pyzx/graph/base.py b/pyzx/graph/base.py
index a37e4de5..cfd10a91 100644
--- a/pyzx/graph/base.py
+++ b/pyzx/graph/base.py
@@ -85,6 +85,7 @@ def __init__(self) -> None:
         self.phase_master: Optional['simplify.Simplifier'] = None
         self.phase_mult: Dict[int,Literal[1,-1]] = dict()
         self.max_phase_index: int = -1
+        self._vdata: Dict[VT,Dict[str,Any]] = dict()
 
         # merge_vdata(v0,v1) is an optional, custom function for merging
         # vdata of v1 into v0 during spider fusion etc.
diff --git a/pyzx/graph/diff.py b/pyzx/graph/diff.py
index 9d253b34..511705ea 100644
--- a/pyzx/graph/diff.py
+++ b/pyzx/graph/diff.py
@@ -32,6 +32,7 @@ class GraphDiff(Generic[VT, ET]):
 	changed_edge_types: Dict[ET, EdgeType.Type]
 	changed_phases: Dict[VT, FractionLike]
 	changed_pos: Dict[VT, Tuple[FloatInt,FloatInt]]
+	changed_vdata: Dict[VT, Any]
 
 	def __init__(self, g1: BaseGraph[VT,ET], g2: BaseGraph[VT,ET]) -> None:
 		self.calculate_diff(g1,g2)