diff --git a/crates/fj-kernel/src/objects/object.rs b/crates/fj-kernel/src/objects/object.rs
index 22c9d16f20..a538400090 100644
--- a/crates/fj-kernel/src/objects/object.rs
+++ b/crates/fj-kernel/src/objects/object.rs
@@ -31,6 +31,15 @@ macro_rules! object {
                     )*
                 }
             }
+
+            /// Validate the object
+            pub fn validate(&self, errors: &mut Vec<ValidationError>) {
+                match self {
+                    $(
+                        Self::$ty(object) => object.validate(errors),
+                    )*
+                }
+            }
         }
 
         impl Object<WithHandle> {
@@ -47,15 +56,6 @@ macro_rules! object {
                     )*
                 }
             }
-
-            /// Validate the object
-            pub fn validate(&self, errors: &mut Vec<ValidationError>) {
-                match self {
-                    $(
-                        Self::$ty((_, object)) => object.validate(errors),
-                    )*
-                }
-            }
         }
 
         impl From<Object<WithHandle>> for Object<BehindHandle> {
diff --git a/crates/fj-kernel/src/services/mod.rs b/crates/fj-kernel/src/services/mod.rs
index 561a5acfc7..79482136d2 100644
--- a/crates/fj-kernel/src/services/mod.rs
+++ b/crates/fj-kernel/src/services/mod.rs
@@ -11,7 +11,7 @@ use crate::objects::{Object, Objects, WithHandle};
 pub use self::{
     objects::{InsertObject, Operation},
     service::{Service, State},
-    validation::{Validation, ValidationFailed},
+    validation::{Validation, ValidationCommand, ValidationEvent},
 };
 
 /// The kernel services
@@ -46,7 +46,10 @@ impl Services {
             .execute(Operation::InsertObject { object }, &mut object_events);
 
         for object_event in object_events {
-            self.validation.execute(object_event, &mut Vec::new());
+            let command = ValidationCommand::ValidateObject {
+                object: object_event.object.into(),
+            };
+            self.validation.execute(command, &mut Vec::new());
         }
     }
 }
diff --git a/crates/fj-kernel/src/services/validation.rs b/crates/fj-kernel/src/services/validation.rs
index 5e0717a8f5..326ff87383 100644
--- a/crates/fj-kernel/src/services/validation.rs
+++ b/crates/fj-kernel/src/services/validation.rs
@@ -6,23 +6,25 @@ use crate::{
     validate::ValidationError,
 };
 
-use super::{objects::InsertObject, State};
+use super::State;
 
 /// Errors that occurred while validating the objects inserted into the stores
 #[derive(Default)]
-pub struct Validation(pub BTreeMap<ObjectId, ValidationFailed>);
+pub struct Validation {
+    errors: BTreeMap<ObjectId, ValidationError>,
+}
 
 impl Drop for Validation {
     fn drop(&mut self) {
-        let num_errors = self.0.len();
+        let num_errors = self.errors.len();
         if num_errors > 0 {
             println!(
                 "Dropping `Validation` with {num_errors} unhandled validation \
                 errors:"
             );
 
-            for event in self.0.values() {
-                println!("{}", event.err);
+            for err in self.errors.values() {
+                println!("{}", err);
             }
 
             if !thread::panicking() {
@@ -33,32 +35,50 @@ impl Drop for Validation {
 }
 
 impl State for Validation {
-    type Command = InsertObject;
-    type Event = ValidationFailed;
+    type Command = ValidationCommand;
+    type Event = ValidationEvent;
 
     fn decide(&self, command: Self::Command, events: &mut Vec<Self::Event>) {
+        let ValidationCommand::ValidateObject { object } = command;
+
         let mut errors = Vec::new();
-        command.object.validate(&mut errors);
+        object.validate(&mut errors);
 
         for err in errors {
-            events.push(ValidationFailed {
-                object: command.object.clone().into(),
+            events.push(ValidationEvent::ValidationFailed {
+                object: object.clone(),
                 err,
             });
         }
     }
 
     fn evolve(&mut self, event: &Self::Event) {
-        self.0.insert(event.object.id(), event.clone());
+        match event {
+            ValidationEvent::ValidationFailed { object, err } => {
+                self.errors.insert(object.id(), err.clone());
+            }
+        }
     }
 }
 
-/// An event produced by the validation service
+/// The command accepted by the validation service
+pub enum ValidationCommand {
+    /// Validate the provided object
+    ValidateObject {
+        /// The object to validate
+        object: Object<BehindHandle>,
+    },
+}
+
+/// The event produced by the validation service
 #[derive(Clone)]
-pub struct ValidationFailed {
-    /// The object for which validation failed
-    pub object: Object<BehindHandle>,
+pub enum ValidationEvent {
+    /// Validation of an object failed
+    ValidationFailed {
+        /// The object for which validation failed
+        object: Object<BehindHandle>,
 
-    /// The validation error
-    pub err: ValidationError,
+        /// The validation error
+        err: ValidationError,
+    },
 }