diff --git a/packages/common/src/data/Todo.class.ts b/packages/common/src/data/Todo.class.ts
index a12d40e..d41a559 100644
--- a/packages/common/src/data/Todo.class.ts
+++ b/packages/common/src/data/Todo.class.ts
@@ -9,7 +9,7 @@ export class Todo
         _kind:      Kind("Todo"),
         _tag:       Tag("Todo"),
 
-        id:         S.String,
+        id:         S.OptionFromSelf(S.String),
         title:      S.String,
         content:    S.String,
 
@@ -26,6 +26,7 @@ export class Todo
 export const JsonifiableTodo = Todo.pipe(Jsonifiable(S.Struct({
     ...Todo.fields,
 
+    id:         S.OptionFromNullOr(S.String),
     due:        S.OptionFromNullOr(S.DateFromString),
     createdAt:  S.DateFromString,
     updatedAt:  S.DateFromString,
diff --git a/packages/common/src/traits/Identifiable.trait.ts b/packages/common/src/traits/Identifiable.trait.ts
index 9a5972a..34fc704 100644
--- a/packages/common/src/traits/Identifiable.trait.ts
+++ b/packages/common/src/traits/Identifiable.trait.ts
@@ -1,4 +1,4 @@
-import { Equal } from "effect"
+import { Equal, Option } from "effect"
 
 
 export interface Identifiable<
@@ -6,7 +6,7 @@ export interface Identifiable<
     ID,
 > {
     readonly _kind:  Kind
-    readonly id:     ID
+    readonly id:     Option.Option<ID>
 }
 
 export module Identifiable {
@@ -17,6 +17,9 @@ export module Identifiable {
         that:  Identifiable<Kind, ID>,
         to:    Identifiable<Kind, ID>,
     ): boolean {
-        return Equal.equals(that.id, to.id)
+        // Two elements can only be equal if they both have a defined ID
+        return Option.isSome(that.id) && Option.isSome(to.id)
+            ? Equal.equals(that.id, to.id)
+            : false
     }
 }