diff --git a/index.d.ts b/index.d.ts
index 7412fcf..39ce5b9 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -1,5 +1,4 @@
-declare function deepmerge<T>(x: Partial<T>, y: Partial<T>, options?: deepmerge.Options): T;
-declare function deepmerge<T1, T2>(x: Partial<T1>, y: Partial<T2>, options?: deepmerge.Options): T1 & T2;
+declare function deepmerge<T1, T2>(x: T1, y: T2, options?: deepmerge.Options): T1 & T2;
 
 declare namespace deepmerge {
 	export interface Options {
@@ -9,8 +8,11 @@ declare namespace deepmerge {
 		isMergeableObject?(value: object): boolean;
 	}
 
-	export function all (objects: object[], options?: Options): object;
-	export function all<T> (objects: Partial<T>[], options?: Options): T;
+	export function all<T1, T2> (objects: [T1, T2], options?: Options): T1 & T2;
+	export function all<T1, T2, T3> (objects: [T1, T2, T3], options?: Options): T1 & T2 & T3;
+	export function all<T1, T2, T3, T4> (objects: [T1, T2, T3, T4], options?: Options): T1 & T2 & T3 & T4;
+	export function all<T1, T2, T3, T4, T5> (objects: [T1, T2, T3, T4, T5], options?: Options): T1 & T2 & T3 & T4 & T5;
+	export function all<T> (objects: T[], options?: Options): T;
 }
 
 export = deepmerge;
diff --git a/test/typescript.ts b/test/typescript.ts
index 23d2c5c..2ceafdf 100644
--- a/test/typescript.ts
+++ b/test/typescript.ts
@@ -1,33 +1,66 @@
 import * as merge from '../';
 
-const x = {
+let x = {
 	foo: 'abc',
 	bar: 'def',
-	wat: 42,
 }
 
-const y = {
+let y = {
 	foo: 'cba',
-	bar: 'fed',
+	baz: 'fed',
 	wat: 42,
 }
 
-const z = {
-	baz: '123',
-	quux: '456',
-	wat: 42,
+let z: {
+	bar: string,
+	baz: string,
+	qux?: string,
+} = {
+	bar: 'a',
+	baz: 'a'
 }
 
-let merged1 = merge(x, y);
-let merged2 = merge(x, z);
-let merged3 = merge.all<{wat: number}>([ x, y, z ]);
+let merged1: {foo: string, bar: string, baz: string, wat: number} = merge(x, y);
+let merged2: {foo: string, bar: string, baz: string, qux?: string} = merge(x, z);
+
+let mergedAll1: {t1: string} = merge.all([
+	{t1: 'a'},
+])
+
+let mergedAll2: {t1: string, t2: string} = merge.all([
+	{t1: 'a'},
+	{t2: 'a'},
+])
+
+let mergedAll3: {t1: string, t2: string, t3: string} = merge.all([
+	{t1: 'a'},
+	{t2: 'a'},
+	{t3: 'a'},
+])
+
+let mergedAll4: {t1: string, t2: string, t3: string, t4: string} = merge.all([
+	{t1: 'a'},
+	{t2: 'a'},
+	{t3: 'a'},
+	{t4: 'a'},
+])
 
-merged1.foo;
-merged1.bar;
-merged2.foo;
-merged2.baz;
-merged3.wat;
+let mergedAll5: {t1: string, t2: string, t3: string, t4: string, t5: string} = merge.all([
+	{t1: 'a'},
+	{t2: 'a'},
+	{t3: 'a'},
+	{t4: 'a'},
+	{t5: 'a'},
+])
 
+let merged6: {t1: string} = merge.all([
+	{t1: 'a'},
+	{t1: 'a'},
+	{t1: 'a'},
+	{t1: 'a'},
+	{t1: 'a'},
+	{t1: 'a'},
+])
 
 const options1: merge.Options = {
 	clone: true,
@@ -60,6 +93,10 @@ const options3: merge.Options = {
 
 merged1 = merge(x, y, options1);
 merged2 = merge(x, z, options2);
-merged3 = merge.all<{wat: number}>([x, y, z], options1);
+mergedAll3 = merge.all([
+	{t1: 'a'},
+	{t2: 'a'},
+	{t3: 'a'},
+], options1)
 
-const merged4 = merge(x, y, options3);
+merged1 = merge(x, y, options3);