diff --git a/types/seamless-immutable/index.d.ts b/types/seamless-immutable/index.d.ts
index f5d3a2c3a3..1990dff0ab 100644
--- a/types/seamless-immutable/index.d.ts
+++ b/types/seamless-immutable/index.d.ts
@@ -96,7 +96,7 @@ declare namespace SeamlessImmutable {
         /** New methods added by seamless-immutable. */
         interface Additions<T> {
             asMutable(opts?: AsMutableOptions): T[];
-            asObject(toKeyValue: (item: T) => [string, any]): Immutable<object>;
+            asObject<U extends object = {}, K extends keyof U = keyof U>(toKeyValue: (item: T) => [K, U[K]]): Immutable<U>;
             flatMap<TTarget>(mapFunction: (item: T) => TTarget): Immutable<TTarget extends any[] ? TTarget : TTarget[]>;
         }
 
diff --git a/types/seamless-immutable/seamless-immutable-tests.ts b/types/seamless-immutable/seamless-immutable-tests.ts
index 5b1a33d0bb..1e54f9eff6 100644
--- a/types/seamless-immutable/seamless-immutable-tests.ts
+++ b/types/seamless-immutable/seamless-immutable-tests.ts
@@ -155,7 +155,10 @@ interface ExtendedUser extends User {
     );
 
     // asObject
-    const arrayToObject1: Immutable.Immutable<object> = array.asObject((value) => [value.toString(), value]);
+    interface ArrayToObjectResult {
+        theFirstName: string;
+    }
+    const arrayToObject1: Immutable.Immutable<ArrayToObjectResult> = array.asObject<ArrayToObjectResult>((value) => ['theFirstName', value.firstName]);
 }
 
 //