diff --git a/src/configuration.ts b/src/configuration.ts
index 1dbd4de8..f891b8a6 100644
--- a/src/configuration.ts
+++ b/src/configuration.ts
@@ -1,12 +1,15 @@
 import type * as http from 'node:http';
 
-import { ERRORS } from './errors.js';
+import { HttpProxyMiddlewareError } from './errors.js';
 import type { Options } from './types.js';
 
 export function verifyConfig<TReq extends http.IncomingMessage, TRes extends http.ServerResponse>(
   options: Options<TReq, TRes>,
 ): void {
   if (!options.target && !options.router) {
-    throw new Error(ERRORS.ERR_CONFIG_FACTORY_TARGET_MISSING);
+    throw new HttpProxyMiddlewareError(
+      '[HPM] Missing "target" option. Example: {target: "http://www.example.org"}',
+      'ERR_CONFIG_FACTORY_TARGET_MISSING',
+    );
   }
 }
diff --git a/src/errors.ts b/src/errors.ts
index c9e337d0..4bc60863 100644
--- a/src/errors.ts
+++ b/src/errors.ts
@@ -1,10 +1,3 @@
-export enum ERRORS {
-  ERR_CONFIG_FACTORY_TARGET_MISSING = '[HPM] Missing "target" option. Example: {target: "http://www.example.org"}',
-  ERR_CONTEXT_MATCHER_GENERIC = '[HPM] Invalid pathFilter. Expecting something like: "/api" or ["/api", "/ajax"]',
-  ERR_CONTEXT_MATCHER_INVALID_ARRAY = '[HPM] Invalid pathFilter. Plain paths (e.g. "/api") can not be mixed with globs (e.g. "/api/**"). Expecting something like: ["/api", "/ajax"] or ["/api/**", "!**.html"].',
-  ERR_PATH_REWRITER_CONFIG = '[HPM] Invalid pathRewrite config. Expecting object with pathRewrite config or a rewrite function',
-}
-
 export class HttpProxyMiddlewareError extends Error {
   code: string;
 
diff --git a/src/handlers/fix-request-body-utils/stringify-form-data.ts b/src/handlers/fix-request-body-utils/stringify-form-data.ts
index 58689901..09fca347 100644
--- a/src/handlers/fix-request-body-utils/stringify-form-data.ts
+++ b/src/handlers/fix-request-body-utils/stringify-form-data.ts
@@ -1,7 +1,12 @@
 import { HttpProxyMiddlewareError } from '../../errors.js';
 
 const CR_OR_LF = /[\r\n]/;
-const ERROR_CODE_PREFIX = 'HPM_ERR_INVALID_MULTIPART';
+
+/**
+ * HPM_ERR_INVALID_MULTIPART prefixed error code will be used in
+ * [status-code.ts]({@link ../../status-code.ts}) to return status code 400.
+ */
+export const HPM_ERR_INVALID_MULTIPART = 'HPM_ERR_INVALID_MULTIPART';
 
 /**
  * stringify FormData data
@@ -35,7 +40,7 @@ function getMultipartBoundary(contentType: string): string {
   if (!boundary || CR_OR_LF.test(boundary)) {
     throw new HttpProxyMiddlewareError(
       '[HPM] invalid multipart boundary detected.',
-      `${ERROR_CODE_PREFIX}_BOUNDARY`,
+      `${HPM_ERR_INVALID_MULTIPART}_BOUNDARY`,
     );
   }
 
@@ -48,14 +53,14 @@ function validateMultipartField(fieldName: string, fieldValue: string, boundary:
   if (CR_OR_LF.test(fieldName)) {
     throw new HttpProxyMiddlewareError(
       `[HPM] invalid multipart field name "${fieldName}" detected.`,
-      `${ERROR_CODE_PREFIX}_FIELD_NAME`,
+      `${HPM_ERR_INVALID_MULTIPART}_FIELD_NAME`,
     );
   }
 
   if (CR_OR_LF.test(fieldValue) || fieldValue.includes(boundaryDelimiter)) {
     throw new HttpProxyMiddlewareError(
       `[HPM] invalid multipart field value for "${fieldName}" detected.`,
-      `${ERROR_CODE_PREFIX}_FIELD_VALUE`,
+      `${HPM_ERR_INVALID_MULTIPART}_FIELD_VALUE`,
     );
   }
 }
diff --git a/src/path-filter.ts b/src/path-filter.ts
index 9790336b..d5ed2e6f 100644
--- a/src/path-filter.ts
+++ b/src/path-filter.ts
@@ -3,7 +3,7 @@ import type * as http from 'node:http';
 import isGlob from 'is-glob';
 import micromatch from 'micromatch';
 
-import { ERRORS } from './errors.js';
+import { HttpProxyMiddlewareError } from './errors.js';
 import type { Filter } from './types.js';
 
 export function matchPathFilter<TReq extends http.IncomingMessage = http.IncomingMessage>(
@@ -30,7 +30,10 @@ export function matchPathFilter<TReq extends http.IncomingMessage = http.Incomin
       return matchMultiGlobPath(pathFilter as string[], uri);
     }
 
-    throw new Error(ERRORS.ERR_CONTEXT_MATCHER_INVALID_ARRAY);
+    throw new HttpProxyMiddlewareError(
+      '[HPM] Invalid pathFilter. Plain paths (e.g. "/api") can not be mixed with globs (e.g. "/api/**"). Expecting something like: ["/api", "/ajax"] or ["/api/**", "!**.html"].',
+      'HPM_INVALID_PATH_FILTER_ARRAY_CONFIG',
+    );
   }
 
   // custom matching
@@ -39,7 +42,10 @@ export function matchPathFilter<TReq extends http.IncomingMessage = http.Incomin
     return Boolean(pathFilter(pathname, req as TReq));
   }
 
-  throw new Error(ERRORS.ERR_CONTEXT_MATCHER_GENERIC);
+  throw new HttpProxyMiddlewareError(
+    '[HPM] Invalid pathFilter. Expecting something like: "/api" or ["/api", "/ajax"]',
+    'HPM_INVALID_PATH_FILTER_CONFIG',
+  );
 }
 
 /**
diff --git a/src/path-rewriter.ts b/src/path-rewriter.ts
index 78e031e7..8a6f7a65 100644
--- a/src/path-rewriter.ts
+++ b/src/path-rewriter.ts
@@ -3,7 +3,7 @@ import type { IncomingMessage, ServerResponse } from 'node:http';
 import isPlainObject from 'is-plain-obj';
 
 import { Debug } from './debug.js';
-import { ERRORS } from './errors.js';
+import { HttpProxyMiddlewareError } from './errors.js';
 import type { PathRewriteConfig } from './types.js';
 
 const debug = Debug.extend('path-rewriter');
@@ -57,7 +57,10 @@ function isValidRewriteConfig<
   } else if (rewriteConfig === undefined || rewriteConfig === null) {
     return false;
   } else {
-    throw new Error(ERRORS.ERR_PATH_REWRITER_CONFIG);
+    throw new HttpProxyMiddlewareError(
+      '[HPM] Invalid pathRewrite config. Expecting object with pathRewrite config or a rewrite function',
+      'HPM_INVALID_PATH_REWRITER_CONFIG',
+    );
   }
 }
 
diff --git a/test/unit/configuration.spec.ts b/test/unit/configuration.spec.ts
index 66b4057f..54da78eb 100644
--- a/test/unit/configuration.spec.ts
+++ b/test/unit/configuration.spec.ts
@@ -1,6 +1,7 @@
 import { beforeEach, describe, expect, it } from 'vitest';
 
 import { verifyConfig } from '../../src/configuration.js';
+import { HttpProxyMiddlewareError } from '../../src/errors.js';
 
 describe('configFactory', () => {
   describe('verifyConfig()', () => {
@@ -14,7 +15,8 @@ describe('configFactory', () => {
       });
 
       it('should throw an error when target and router option are missing', () => {
-        expect(fn).toThrow(Error);
+        expect(fn).toThrow(HttpProxyMiddlewareError);
+        expect(fn).toThrow(expect.objectContaining({ code: 'ERR_CONFIG_FACTORY_TARGET_MISSING' }));
       });
     });
 
diff --git a/test/unit/path-filter.spec.ts b/test/unit/path-filter.spec.ts
index fbab8e40..2c813458 100644
--- a/test/unit/path-filter.spec.ts
+++ b/test/unit/path-filter.spec.ts
@@ -1,5 +1,6 @@
 import { beforeEach, describe, expect, it } from 'vitest';
 
+import { HttpProxyMiddlewareError } from '../../src/errors.js';
 import { matchPathFilter } from '../../src/path-filter.js';
 import { createMockRequest } from '../test-utils.js';
 
@@ -215,19 +216,31 @@ describe('Path Filter', () => {
 
     describe('Throw error', () => {
       it('should throw error with null', () => {
-        expect(testPathFilter(null)).toThrow(Error);
+        expect(testPathFilter(null)).toThrow(HttpProxyMiddlewareError);
+        expect(testPathFilter(null)).toThrow(
+          expect.objectContaining({ code: 'HPM_INVALID_PATH_FILTER_CONFIG' }),
+        );
       });
 
       it('should throw error with object literal', () => {
-        expect(testPathFilter(mockReq)).toThrow(Error);
+        expect(testPathFilter(mockReq)).toThrow(HttpProxyMiddlewareError);
+        expect(testPathFilter(mockReq)).toThrow(
+          expect.objectContaining({ code: 'HPM_INVALID_PATH_FILTER_CONFIG' }),
+        );
       });
 
       it('should throw error with integers', () => {
-        expect(testPathFilter(123)).toThrow(Error);
+        expect(testPathFilter(123)).toThrow(HttpProxyMiddlewareError);
+        expect(testPathFilter(123)).toThrow(
+          expect.objectContaining({ code: 'HPM_INVALID_PATH_FILTER_CONFIG' }),
+        );
       });
 
       it('should throw error with mixed string and glob pattern', () => {
-        expect(testPathFilter(['/api', '!*.html'])).toThrow(Error);
+        expect(testPathFilter(['/api', '!*.html'])).toThrow(HttpProxyMiddlewareError);
+        expect(testPathFilter(['/api', '!*.html'])).toThrow(
+          expect.objectContaining({ code: 'HPM_INVALID_PATH_FILTER_ARRAY_CONFIG' }),
+        );
       });
     });
 
diff --git a/test/unit/path-rewriter.spec.ts b/test/unit/path-rewriter.spec.ts
index bc5ff68e..49219334 100644
--- a/test/unit/path-rewriter.spec.ts
+++ b/test/unit/path-rewriter.spec.ts
@@ -1,5 +1,6 @@
 import { beforeEach, describe, expect, it, vi } from 'vitest';
 
+import { HttpProxyMiddlewareError } from '../../src/errors.js';
 import { createPathRewriter } from '../../src/path-rewriter.js';
 import type { Options } from '../../src/types.js';
 import type { PathRewriteConfig } from '../../src/types.js';
@@ -150,10 +151,14 @@ describe('Path rewriting', () => {
     });
 
     it('should throw when bad config is provided', () => {
-      expect(badFn(123 as unknown as PathRewriteConfig)).toThrow(Error);
-      expect(badFn('abc' as unknown as PathRewriteConfig)).toThrow(Error);
-      expect(badFn([] as unknown as PathRewriteConfig)).toThrow(Error);
-      expect(badFn([1, 2, 3] as unknown as PathRewriteConfig)).toThrow(Error);
+      expect(badFn(123 as unknown as PathRewriteConfig)).toThrow(HttpProxyMiddlewareError);
+      expect(badFn('abc' as unknown as PathRewriteConfig)).toThrow(
+        expect.objectContaining({ code: 'HPM_INVALID_PATH_REWRITER_CONFIG' }),
+      );
+      expect(badFn([] as unknown as PathRewriteConfig)).toThrow(HttpProxyMiddlewareError);
+      expect(badFn([1, 2, 3] as unknown as PathRewriteConfig)).toThrow(
+        expect.objectContaining({ code: 'HPM_INVALID_PATH_REWRITER_CONFIG' }),
+      );
     });
 
     it('should not throw when empty Object config is provided', () => {