diff --git a/README.md b/README.md
index bbc494c..e403ec6 100644
--- a/README.md
+++ b/README.md
@@ -17,10 +17,10 @@ import { n } from '@haaxor1689/nil';
 const mySchema = n.string(14);
 
 // Parse into Uint8Array
-const buffer = mySchema.toBuffer('Hello world!!!');
+const buffer = await mySchema.toBuffer('Hello world!!!');
 
 // Prase from Uint8Array
-const parsed = mySchema.fromBuffer(buffer);
+const parsed = await mySchema.fromBuffer(buffer);
 ```
 
 Creating an object schema
@@ -36,10 +36,10 @@ const User = n.object({
 type User = n.output<typeof User>;
 // { username: string; age: number; active: boolean; }
 
-const buffer = User.toBuffer({ username: 'Jane', age: 30, active: true });
+const buffer = await User.toBuffer({ username: 'Jane', age: 30, active: true });
 
 // Prase from Uint8Array
-User.fromBuffer(buffer);
+await User.fromBuffer(buffer);
 ```
 
 ## Primitives
@@ -231,8 +231,8 @@ All Nil schemas contain these methods.
 
 ```ts
 .transform(
-  afterDecode: (v: Input, ctx?: ParseContext) => Output,
-  beforeEncode: (v: Output, ctx?: ParseContext) => Input
+  afterDecode: (v: Input, ctx?: ParseContext) => Promise<Output>,
+  beforeEncode: (v: Output, ctx?: ParseContext) => Promise<Input>
 )
 ```
 
@@ -256,7 +256,7 @@ const MySchema = n
 type MySchema = z.output<typeof MySchema>;
 
 // Resulting buffer will start with correct `itemCount` number
-MySchema.toBuffer([1, 2, 3, 4]);
+await MySchema.toBuffer([1, 2, 3, 4]);
 ```
 
 You can also access the current context when creating transformations to reference other attributes from the parent type (if any). The easiest way to do this is by using the `resolvePath` helper function.
@@ -282,7 +282,7 @@ const MySchema = n.object({
 ### `.fromBuffer`
 
 ```ts
-.fromBuffer(data: Uint8Array): Output
+.fromBuffer(data: Uint8Array): Promise<Output>
 ```
 
 Tries to parse given buffer into output type of used schema. Throws errors on failure.
@@ -290,7 +290,7 @@ Tries to parse given buffer into output type of used schema. Throws errors on fa
 ### `.toBuffer`
 
 ```ts
-.toBuffer(value: Output): Uint8Array
+.toBuffer(value: Output): Promise<Uint8Array>
 ```
 
 Tries to serialize a given object into a buffer.
diff --git a/package.json b/package.json
index 925df4c..88f6a84 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
 	"name": "@haaxor1689/nil",
-	"version": "0.1.2",
+	"version": "0.1.3",
 	"description": "TypeScript-first binary data parsing library with static type inference",
 	"author": "Maroš Beťko <betkomaros@gmail.com>",
 	"repository": {
diff --git a/src/helpers/util.ts b/src/helpers/util.ts
index f041b7d..2146a7f 100644
--- a/src/helpers/util.ts
+++ b/src/helpers/util.ts
@@ -11,16 +11,16 @@ export type identity<T> = T;
 export type flatten<T> = identity<{ [k in keyof T]: T[k] }>;
 
 // FIXME: Improve types
-type ObjectMapper<T, U> = (value: T, key: string) => U;
-export const mapValues = <T, U>(
+type ObjectMapper<T, U> = (value: T, key: string) => Promise<U>;
+export const mapValues = async <T, U>(
 	obj: Record<string, T>,
 	mapper: ObjectMapper<T, U>
-): Record<string, U> => {
+): Promise<Record<string, U>> => {
 	const result: Record<string, U> = {};
 
 	for (const key in obj) {
 		if (Object.prototype.hasOwnProperty.call(obj, key)) {
-			result[key] = mapper(obj[key], key);
+			result[key] = await mapper(obj[key], key);
 		}
 	}
 
diff --git a/src/types.ts b/src/types.ts
index 87666ae..6d1d0f5 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -32,24 +32,24 @@ export abstract class NilType<Output = any, Def = object, Input = Output> {
 	abstract _decode(data: DataView, ctx?: ParseContext): Input;
 	abstract _encode(data: DataView, value: Input, ctx?: ParseContext): void;
 
-	_afterDecode(value: Input, _ctx?: ParseContext): Output {
+	async _afterDecode(value: Input, _ctx?: ParseContext): Promise<Output> {
 		return value as never;
 	}
 
-	_beforeEncode(value: Output, _ctx?: ParseContext): Input {
+	async _beforeEncode(value: Output, _ctx?: ParseContext): Promise<Input> {
 		return value as never;
 	}
 
 	abstract size(value?: Input, ctx?: ParseContext): number;
 
-	fromBuffer(data: Uint8Array): Output {
+	async fromBuffer(data: Uint8Array): Promise<Output> {
 		const view = new DataView(data.buffer);
 		const val = this._decode(view);
-		return this._afterDecode(val);
+		return await this._afterDecode(val);
 	}
 
-	toBuffer(value: Output): Uint8Array {
-		const val = this._beforeEncode(value);
+	async toBuffer(value: Output): Promise<Uint8Array> {
+		const val = await this._beforeEncode(value);
 		const buffer = new Uint8Array(this.size(val));
 		const view = new DataView(buffer.buffer);
 		this._encode(view, val);
@@ -89,14 +89,14 @@ class NilEffects<
 		this._def.schema._encode(data, value, ctx);
 	}
 
-	_afterDecode(value: Input, ctx?: ParseContext): Output {
+	async _afterDecode(value: Input, ctx?: ParseContext): Promise<Output> {
 		const { schema } = this._def;
-		return this._def.transform[0](schema._afterDecode(value, ctx), ctx);
+		return this._def.transform[0](await schema._afterDecode(value, ctx), ctx);
 	}
 
-	_beforeEncode(value: Output, ctx?: ParseContext): Input {
+	async _beforeEncode(value: Output, ctx?: ParseContext): Promise<Input> {
 		const { schema } = this._def;
-		return schema._beforeEncode(this._def.transform[1](value, ctx), ctx);
+		return await schema._beforeEncode(this._def.transform[1](value, ctx), ctx);
 	}
 }
 
@@ -365,30 +365,37 @@ class NilArray<T extends NilTypeAny> extends NilType<
 		});
 	}
 
-	_afterDecode(value: T['_input'][], ctx?: ParseContext) {
+	async _afterDecode(value: T['_input'][], ctx?: ParseContext) {
 		const { schema } = this._def;
-		return value.map((v, i) => {
+
+		const arr = [];
+		for (let i = 0; i < value.length; i++) {
+			const v = value[i];
 			const newCtx: ParseContext = {
 				// FIXME: Types
 				value: value as never,
 				path: [...(ctx?.path ?? []), i],
 				parent: ctx
 			};
-			return schema._afterDecode(v, newCtx);
-		});
+			arr.push(await schema._afterDecode(v, newCtx));
+		}
+		return arr;
 	}
 
-	_beforeEncode(value: T['_output'][], ctx?: ParseContext) {
+	async _beforeEncode(value: T['_output'][], ctx?: ParseContext) {
 		const { schema } = this._def;
-		return value.map((v, i) => {
+		const arr = [];
+		for (let i = 0; i < value.length; i++) {
+			const v = value[i];
 			const newCtx: ParseContext = {
 				// FIXME: Types
 				value: value as never,
 				path: [...(ctx?.path ?? []), i],
 				parent: ctx
 			};
-			return schema._beforeEncode(v, newCtx);
-		});
+			arr.push(await schema._beforeEncode(v, newCtx));
+		}
+		return arr;
 	}
 
 	#elementSize(value?: T['_input'][], ctx?: ParseContext) {
@@ -488,7 +495,7 @@ class NilObject<
 				parent: ctx
 			};
 			return v._afterDecode(value[k as keyof Input], newCtx);
-		}) as Output;
+		}) as Promise<Output>;
 	}
 
 	_beforeEncode(value: Output, ctx?: ParseContext) {
@@ -501,7 +508,7 @@ class NilObject<
 				parent: ctx
 			};
 			return v._beforeEncode(value[k as keyof Output], newCtx);
-		}) as Input;
+		}) as Promise<Input>;
 	}
 }
 
@@ -574,7 +581,7 @@ export class NilEnum<
 		this._def.type._encode(data, value);
 	}
 
-	_afterDecode(value: T['_input']): O[number] {
+	async _afterDecode(value: T['_input']) {
 		const option = this._def.options[value];
 		if (option === undefined)
 			throw new Error(
@@ -583,7 +590,7 @@ export class NilEnum<
 		return option;
 	}
 
-	_beforeEncode(value: O[number]): T['_input'] {
+	async _beforeEncode(value: O[number]) {
 		const index = this._def.options.indexOf(value);
 		if (index === -1)
 			throw new Error(