diff --git a/hugr-core/src/extension/resolution.rs b/hugr-core/src/extension/resolution.rs
index 4901502b9..269924a45 100644
--- a/hugr-core/src/extension/resolution.rs
+++ b/hugr-core/src/extension/resolution.rs
@@ -44,11 +44,8 @@ pub fn resolve_type_extensions<RV: MaybeRV>(
     typ: &mut TypeBase<RV>,
     extensions: &ExtensionRegistry,
 ) -> Result<(), ExtensionResolutionError> {
-    // This public export is used for implementing `CustomConst::update_extensions`, so we don't need the full internal API here.
-    // TODO: Make `node` optional in `ExtensionResolutionError`
-    let node: Node = portgraph::NodeIndex::new(0).into();
     let mut used_extensions = ExtensionRegistry::default();
-    resolve_type_exts(node, typ, extensions, &mut used_extensions)
+    resolve_type_exts(None, typ, extensions, &mut used_extensions)
 }
 
 /// Update all weak Extension pointers in a custom type.
@@ -56,11 +53,8 @@ pub fn resolve_custom_type_extensions(
     typ: &mut CustomType,
     extensions: &ExtensionRegistry,
 ) -> Result<(), ExtensionResolutionError> {
-    // This public export is used for implementing `CustomConst::update_extensions`, so we don't need the full internal API here.
-    // TODO: Make `node` optional in `ExtensionResolutionError`
-    let node: Node = portgraph::NodeIndex::new(0).into();
     let mut used_extensions = ExtensionRegistry::default();
-    resolve_custom_type_exts(node, typ, extensions, &mut used_extensions)
+    resolve_custom_type_exts(None, typ, extensions, &mut used_extensions)
 }
 
 /// Update all weak Extension pointers inside a type argument.
@@ -68,11 +62,8 @@ pub fn resolve_typearg_extensions(
     arg: &mut TypeArg,
     extensions: &ExtensionRegistry,
 ) -> Result<(), ExtensionResolutionError> {
-    // This public export is used for implementing `CustomConst::update_extensions`, so we don't need the full internal API here.
-    // TODO: Make `node` optional in `ExtensionResolutionError`
-    let node: Node = portgraph::NodeIndex::new(0).into();
     let mut used_extensions = ExtensionRegistry::default();
-    resolve_typearg_exts(node, arg, extensions, &mut used_extensions)
+    resolve_typearg_exts(None, arg, extensions, &mut used_extensions)
 }
 
 /// Update all weak Extension pointers inside a constant value.
@@ -80,11 +71,8 @@ pub fn resolve_value_extensions(
     value: &mut Value,
     extensions: &ExtensionRegistry,
 ) -> Result<(), ExtensionResolutionError> {
-    // This public export is used for implementing `CustomConst::update_extensions`, so we don't need the full internal API here.
-    // TODO: Make `node` optional in `ExtensionResolutionError`
-    let node: Node = portgraph::NodeIndex::new(0).into();
     let mut used_extensions = ExtensionRegistry::default();
-    resolve_value_exts(node, value, extensions, &mut used_extensions)
+    resolve_value_exts(None, value, extensions, &mut used_extensions)
 }
 
 /// Errors that can occur during extension resolution.
@@ -97,12 +85,13 @@ pub enum ExtensionResolutionError {
     OpaqueOpError(OpaqueOpError),
     /// An operation requires an extension that is not in the given registry.
     #[display(
-        "{op} ({node}) requires extension {missing_extension}, but it could not be found in the extension list used during resolution. The available extensions are: {}",
+        "{op}{} requires extension {missing_extension}, but it could not be found in the extension list used during resolution. The available extensions are: {}",
+        node.map(|n| format!(" in {}", n)).unwrap_or_default(),
         available_extensions.join(", ")
     )]
     MissingOpExtension {
         /// The node that requires the extension.
-        node: Node,
+        node: Option<Node>,
         /// The operation that requires the extension.
         op: OpName,
         /// The missing extension
@@ -111,13 +100,14 @@ pub enum ExtensionResolutionError {
         available_extensions: Vec<ExtensionId>,
     },
     #[display(
-        "Type {ty} in {node} requires extension {missing_extension}, but it could not be found in the extension list used during resolution. The available extensions are: {}",
+        "Type {ty}{} requires extension {missing_extension}, but it could not be found in the extension list used during resolution. The available extensions are: {}",
+        node.map(|n| format!(" in {}", n)).unwrap_or_default(),
         available_extensions.join(", ")
     )]
     /// A type references an extension that is not in the given registry.
     MissingTypeExtension {
         /// The node that requires the extension.
-        node: Node,
+        node: Option<Node>,
         /// The type that requires the extension.
         ty: TypeName,
         /// The missing extension
@@ -138,7 +128,7 @@ pub enum ExtensionResolutionError {
 impl ExtensionResolutionError {
     /// Create a new error for missing operation extensions.
     pub fn missing_op_extension(
-        node: Node,
+        node: Option<Node>,
         op: &OpType,
         missing_extension: &ExtensionId,
         extensions: &ExtensionRegistry,
@@ -153,7 +143,7 @@ impl ExtensionResolutionError {
 
     /// Create a new error for missing type extensions.
     pub fn missing_type_extension(
-        node: Node,
+        node: Option<Node>,
         ty: &TypeName,
         missing_extension: &ExtensionId,
         extensions: &ExtensionRegistry,
diff --git a/hugr-core/src/extension/resolution/ops.rs b/hugr-core/src/extension/resolution/ops.rs
index 8e9591688..4ffc9c35e 100644
--- a/hugr-core/src/extension/resolution/ops.rs
+++ b/hugr-core/src/extension/resolution/ops.rs
@@ -124,7 +124,10 @@ fn operation_extension<'e>(
     match extensions.get(ext) {
         Some(e) => Ok(Some(e)),
         None => Err(ExtensionResolutionError::missing_op_extension(
-            node, op, ext, extensions,
+            Some(node),
+            op,
+            ext,
+            extensions,
         )),
     }
 }
diff --git a/hugr-core/src/extension/resolution/test.rs b/hugr-core/src/extension/resolution/test.rs
index 0cf9fb0dc..73e7cedb9 100644
--- a/hugr-core/src/extension/resolution/test.rs
+++ b/hugr-core/src/extension/resolution/test.rs
@@ -54,7 +54,8 @@ fn resolve_type_extensions(#[case] op: impl Into<OpType>, #[case] extensions: Ex
 
     let mut used_exts = ExtensionRegistry::default();
     resolve_op_extensions(dummy_node, &mut deser_op, &extensions).unwrap();
-    resolve_op_types_extensions(dummy_node, &mut deser_op, &extensions, &mut used_exts).unwrap();
+    resolve_op_types_extensions(Some(dummy_node), &mut deser_op, &extensions, &mut used_exts)
+        .unwrap();
 
     let deser_extensions = deser_op.used_extensions().unwrap();
 
diff --git a/hugr-core/src/extension/resolution/types_mut.rs b/hugr-core/src/extension/resolution/types_mut.rs
index 520bf2919..31439603a 100644
--- a/hugr-core/src/extension/resolution/types_mut.rs
+++ b/hugr-core/src/extension/resolution/types_mut.rs
@@ -22,7 +22,7 @@ use crate::Node;
 ///
 /// This is a helper function used right after deserializing a Hugr.
 pub fn resolve_op_types_extensions(
-    node: Node,
+    node: Option<Node>,
     op: &mut OpType,
     extensions: &ExtensionRegistry,
     used_extensions: &mut ExtensionRegistry,
@@ -113,7 +113,7 @@ pub fn resolve_op_types_extensions(
 ///
 /// Adds the extensions used in the signature to the `used_extensions` registry.
 fn resolve_signature_exts(
-    node: Node,
+    node: Option<Node>,
     signature: &mut Signature,
     extensions: &ExtensionRegistry,
     used_extensions: &mut ExtensionRegistry,
@@ -129,7 +129,7 @@ fn resolve_signature_exts(
 ///
 /// Adds the extensions used in the row to the `used_extensions` registry.
 fn resolve_type_row_exts<RV: MaybeRV>(
-    node: Node,
+    node: Option<Node>,
     row: &mut TypeRowBase<RV>,
     extensions: &ExtensionRegistry,
     used_extensions: &mut ExtensionRegistry,
@@ -144,7 +144,7 @@ fn resolve_type_row_exts<RV: MaybeRV>(
 ///
 /// Adds the extensions used in the type to the `used_extensions` registry.
 pub(super) fn resolve_type_exts<RV: MaybeRV>(
-    node: Node,
+    node: Option<Node>,
     typ: &mut TypeBase<RV>,
     extensions: &ExtensionRegistry,
     used_extensions: &mut ExtensionRegistry,
@@ -175,7 +175,7 @@ pub(super) fn resolve_type_exts<RV: MaybeRV>(
 ///
 /// Adds the extensions used in the type to the `used_extensions` registry.
 pub(super) fn resolve_custom_type_exts(
-    node: Node,
+    node: Option<Node>,
     custom: &mut CustomType,
     extensions: &ExtensionRegistry,
     used_extensions: &mut ExtensionRegistry,
@@ -201,7 +201,7 @@ pub(super) fn resolve_custom_type_exts(
 ///
 /// Adds the extensions used in the type to the `used_extensions` registry.
 pub(super) fn resolve_typearg_exts(
-    node: Node,
+    node: Option<Node>,
     arg: &mut TypeArg,
     extensions: &ExtensionRegistry,
     used_extensions: &mut ExtensionRegistry,
@@ -222,7 +222,7 @@ pub(super) fn resolve_typearg_exts(
 ///
 /// Adds the extensions used in the row to the `used_extensions` registry.
 pub(super) fn resolve_value_exts(
-    node: Node,
+    node: Option<Node>,
     value: &mut Value,
     extensions: &ExtensionRegistry,
     used_extensions: &mut ExtensionRegistry,
diff --git a/hugr-core/src/hugr.rs b/hugr-core/src/hugr.rs
index e3392b601..17e2bffd0 100644
--- a/hugr-core/src/hugr.rs
+++ b/hugr-core/src/hugr.rs
@@ -243,7 +243,7 @@ impl Hugr {
             if let Some(extension) = resolve_op_extensions(node, op, extensions)? {
                 used_extensions.register_updated_ref(extension);
             }
-            resolve_op_types_extensions(node, op, extensions, &mut used_extensions)?;
+            resolve_op_types_extensions(Some(node), op, extensions, &mut used_extensions)?;
         }
 
         self.extensions = used_extensions;