diff --git a/src/tagged-union.ts b/src/tagged-union.ts
index da2245e..3071b45 100644
--- a/src/tagged-union.ts
+++ b/src/tagged-union.ts
@@ -1,4 +1,4 @@
-import type { Exact, ValueOf } from "type-fest";
+import type { Exact, UnknownRecord, ValueOf } from "type-fest";
 
 type UnaryFn<T, R> = (shape: T) => R;
 
@@ -98,27 +98,26 @@ interface TaggedUnionMatcherWidening<T extends object, K extends keyof T> {
 
 type HandlerMap = Record<string | number, UnaryFn<never, unknown> | undefined>;
 
-// `object` carries no index signature, so the read needs the assertion; the
-// factory admits only keys whose values are `string | number` tags, so the
-// result is narrowed to the map's key space.
-const tagAt = (shape: object, k: PropertyKey): string | number =>
-    // oxlint-disable-next-line typescript/no-unsafe-type-assertion
-    (shape as Record<PropertyKey, unknown>)[k] as string | number;
-
 const dispatch =
     (k: PropertyKey) =>
     (handlers: HandlerMap, fallback?: UnaryFn<never, unknown>) =>
-    (shape: object): unknown =>
-        (
-            handlers[tagAt(shape, k)] ??
+    (shape: object): unknown => {
+        // `object` carries no index signature, so the read needs the assertion;
+        // the factory admits only keys whose values are `string | number` tags,
+        // so the result is narrowed to the map's key space.
+        // oxlint-disable-next-line typescript/no-unsafe-type-assertion
+        const tag = (shape as UnknownRecord)[k] as string | number;
+        return (
+            handlers[tag] ??
             fallback ??
             (() => {
-                throw new Error(`Unhandled tag: ${String(tagAt(shape, k))}`);
+                throw new Error(`Unhandled tag: ${String(tag)}`);
             })
         )(
             // oxlint-disable-next-line typescript/no-unsafe-type-assertion
             shape as never,
         );
+    };
 
 export const getTaggedUnionMatcher =
     <T extends object>() =>