diff --git a/package.json b/package.json
index f7b44c6..e04bd17 100644
--- a/package.json
+++ b/package.json
@@ -70,7 +70,7 @@
     "access": "public"
   },
   "dependencies": {
-    "@the-minimal/types": "0.4.0",
+    "@the-minimal/types": "0.5.0",
     "@the-minimal/error": "0.1.1"
   }
 }
diff --git a/src/assertions/optional/index.ts b/src/assertions/optional/index.ts
index c3806b9..ec43e84 100644
--- a/src/assertions/optional/index.ts
+++ b/src/assertions/optional/index.ts
@@ -1,4 +1,4 @@
-import type { Assertion, Optional } from "@the-minimal/types";
+import type { Assertion, Maybe } from "@the-minimal/types";
 
 /**
  * Checks if the assertion passes or if the value is undefined.
@@ -15,6 +15,6 @@ import type { Assertion, Optional } from "@the-minimal/types";
  * ```
  */
 export const optional =
-	<$Value>(assertion: Assertion<$Value>): Assertion<Optional<$Value>> =>
+	<$Value>(assertion: Assertion<$Value>): Assertion<Maybe<$Value>> =>
 	(v: unknown) =>
 		v === undefined || (assertion as any)(v);