diff --git a/src/index.js b/src/index.js
index 554dd78..5b1c3ac 100644
--- a/src/index.js
+++ b/src/index.js
@@ -13,11 +13,17 @@ import schema from "./options.json";
 
 /** @typedef {import("schema-utils/declarations/validate").Schema} Schema */
 /** @typedef {import("webpack").Compiler} Compiler */
+/** @typedef {import("webpack").WebpackPluginInstance} WebpackPluginInstance */
 /** @typedef {import("webpack").Compilation} Compilation */
 /** @typedef {import("webpack").sources.Source} Source */
 /** @typedef {import("webpack").Asset} Asset */
 /** @typedef {import("webpack").WebpackError} WebpackError */
 
+/**
+ * @template T
+ * @typedef {T | { valueOf(): T }} WithImplicitCoercion
+ */
+
 /** @typedef {RegExp | string} Rule */
 
 /** @typedef {Rule[] | Rule} Rules */
@@ -41,7 +47,7 @@ import schema from "./options.json";
  * @callback AlgorithmFunction
  * @param {Buffer} input
  * @param {CompressionOptions<T>} options
- * @param {(error: Error, result: string | Buffer) => void} callback
+ * @param {(error: Error | null | undefined, result: WithImplicitCoercion<ArrayBuffer | SharedArrayBuffer> | Uint8Array | ReadonlyArray<number> | WithImplicitCoercion<Uint8Array | ReadonlyArray<number> | string> | WithImplicitCoercion<string> | { [Symbol.toPrimitive](hint: 'string'): string }) => void} callback
  */
 
 /**
@@ -81,6 +87,7 @@ import schema from "./options.json";
 
 /**
  * @template [T=ZlibOptions]
+ * @implements WebpackPluginInstance
  */
 class CompressionPlugin {
   /**
@@ -195,11 +202,11 @@ class CompressionPlugin {
           }
 
           if (!Buffer.isBuffer(result)) {
-            // eslint-disable-next-line no-param-reassign
-            result = Buffer.from(result);
+            // @ts-ignore
+            resolve(Buffer.from(result));
+          } else {
+            resolve(result);
           }
-
-          resolve(result);
         }
       );
     });
diff --git a/types/index.d.ts b/types/index.d.ts
index 7f960cd..686ece8 100644
--- a/types/index.d.ts
+++ b/types/index.d.ts
@@ -2,10 +2,16 @@
 export default CompressionPlugin;
 export type Schema = import("schema-utils/declarations/validate").Schema;
 export type Compiler = import("webpack").Compiler;
+export type WebpackPluginInstance = import("webpack").WebpackPluginInstance;
 export type Compilation = import("webpack").Compilation;
 export type Source = import("webpack").sources.Source;
 export type Asset = import("webpack").Asset;
 export type WebpackError = import("webpack").WebpackError;
+export type WithImplicitCoercion<T> =
+  | T
+  | {
+      valueOf(): T;
+    };
 export type Rule = RegExp | string;
 export type Rules = Rule[] | Rule;
 export type CustomOptions = {
@@ -16,7 +22,27 @@ export type CompressionOptions<T> = InferDefaultType<T>;
 export type AlgorithmFunction<T> = (
   input: Buffer,
   options: CompressionOptions<T>,
-  callback: (error: Error, result: string | Buffer) => void
+  callback: (
+    error: Error | null | undefined,
+    result:
+      | string
+      | ArrayBuffer
+      | SharedArrayBuffer
+      | Uint8Array
+      | readonly number[]
+      | {
+          valueOf(): ArrayBuffer | SharedArrayBuffer;
+        }
+      | {
+          valueOf(): string | Uint8Array | readonly number[];
+        }
+      | {
+          valueOf(): string;
+        }
+      | {
+          [Symbol.toPrimitive](hint: "string"): string;
+        }
+  ) => void
 ) => any;
 export type PathData = {
   [key: string]: any;
@@ -44,10 +70,15 @@ export type InternalPluginOptions<T> = BasePluginOptions<T> & {
 export type ZlibOptions = import("zlib").ZlibOptions;
 /** @typedef {import("schema-utils/declarations/validate").Schema} Schema */
 /** @typedef {import("webpack").Compiler} Compiler */
+/** @typedef {import("webpack").WebpackPluginInstance} WebpackPluginInstance */
 /** @typedef {import("webpack").Compilation} Compilation */
 /** @typedef {import("webpack").sources.Source} Source */
 /** @typedef {import("webpack").Asset} Asset */
 /** @typedef {import("webpack").WebpackError} WebpackError */
+/**
+ * @template T
+ * @typedef {T | { valueOf(): T }} WithImplicitCoercion
+ */
 /** @typedef {RegExp | string} Rule */
 /** @typedef {Rule[] | Rule} Rules */
 /**
@@ -66,7 +97,7 @@ export type ZlibOptions = import("zlib").ZlibOptions;
  * @callback AlgorithmFunction
  * @param {Buffer} input
  * @param {CompressionOptions<T>} options
- * @param {(error: Error, result: string | Buffer) => void} callback
+ * @param {(error: Error | null | undefined, result: WithImplicitCoercion<ArrayBuffer | SharedArrayBuffer> | Uint8Array | ReadonlyArray<number> | WithImplicitCoercion<Uint8Array | ReadonlyArray<number> | string> | WithImplicitCoercion<string> | { [Symbol.toPrimitive](hint: 'string'): string }) => void} callback
  */
 /**
  * @typedef {{[key: string]: any}} PathData
@@ -99,8 +130,11 @@ export type ZlibOptions = import("zlib").ZlibOptions;
  */
 /**
  * @template [T=ZlibOptions]
+ * @implements WebpackPluginInstance
  */
-declare class CompressionPlugin<T = import("zlib").ZlibOptions> {
+declare class CompressionPlugin<T = import("zlib").ZlibOptions>
+  implements WebpackPluginInstance
+{
   /**
    * @param {BasePluginOptions<T>} [options]
    */