diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0a8dabfacb..ed2c3158fc 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -43,6 +43,7 @@
 - Fix: Content-Dispositionのパースでエラーが発生した場合にダウンロードが完了しない問題を修正
 - Fix: API: i/update avatarIdとbannerIdにnullを渡した時、画像がリセットされない問題を修正
 - Fix: 1:1ではない画像のリアクション通知バッジが左や上に寄ってしまっていたのを中央に来るように修正
+- Fix: .wav, .flacが再生できない問題を修正（新しくアップロードされたファイルのみ修正が適用されます）
 
 ## 13.11.3
 
diff --git a/packages/backend/src/const.ts b/packages/backend/src/const.ts
index 6c7f214214..ee1a9a3093 100644
--- a/packages/backend/src/const.ts
+++ b/packages/backend/src/const.ts
@@ -56,6 +56,11 @@ export const FILE_TYPE_BROWSERSAFE = [
 	'audio/webm',
 
 	'audio/aac',
+
+	// see https://github.com/misskey-dev/misskey/pull/10686
+	'audio/flac',
+	'audio/wav',
+	// backward compatibility
 	'audio/x-flac',
 	'audio/vnd.wave',
 ];
diff --git a/packages/backend/src/core/FileInfoService.ts b/packages/backend/src/core/FileInfoService.ts
index e39b134b7e..b6cae5ea75 100644
--- a/packages/backend/src/core/FileInfoService.ts
+++ b/packages/backend/src/core/FileInfoService.ts
@@ -5,7 +5,7 @@ import * as stream from 'node:stream';
 import * as util from 'node:util';
 import { Injectable } from '@nestjs/common';
 import { FSWatcher } from 'chokidar';
-import { fileTypeFromFile } from 'file-type';
+import * as fileType from 'file-type';
 import FFmpeg from 'fluent-ffmpeg';
 import isSvg from 'is-svg';
 import probeImageSize from 'probe-image-size';
@@ -301,21 +301,34 @@ export class FileInfoService {
 		return fs.promises.access(path).then(() => true, () => false);
 	}
 
+	@bindThis
+	public fixMime(mime: string | fileType.MimeType): string {
+		// see https://github.com/misskey-dev/misskey/pull/10686
+		if (mime === "audio/x-flac") {
+			return "audio/flac";
+		}
+		if (mime === "audio/vnd.wave") {
+			return "audio/wav";
+		}
+
+		return mime;
+	}
+
 	/**
 	 * Detect MIME Type and extension
 	 */
 	@bindThis
 	public async detectType(path: string): Promise<{
-	mime: string;
-	ext: string | null;
-}> {
+		mime: string;
+		ext: string | null;
+	}> {
 	// Check 0 byte
 		const fileSize = await this.getFileSize(path);
 		if (fileSize === 0) {
 			return TYPE_OCTET_STREAM;
 		}
 
-		const type = await fileTypeFromFile(path);
+		const type = await fileType.fileTypeFromFile(path);
 
 		if (type) {
 		// XMLはSVGかもしれない
@@ -324,7 +337,7 @@ export class FileInfoService {
 			}
 
 			return {
-				mime: type.mime,
+				mime: this.fixMime(type.mime),
 				ext: type.ext,
 			};
 		}
diff --git a/packages/backend/src/server/FileServerService.ts b/packages/backend/src/server/FileServerService.ts
index aa91d936b1..98329ddffa 100644
--- a/packages/backend/src/server/FileServerService.ts
+++ b/packages/backend/src/server/FileServerService.ts
@@ -454,7 +454,8 @@ export class FileServerService {
 			fileRole: 'original',
 			file,
 			filename: file.name,
-			mime: file.type,
+			// 古いファイルは修正前のmimeを持っているのでできるだけ修正してあげる
+			mime: this.fileInfoService.fixMime(file.type),
 			ext: null,
 			path,
 		};
diff --git a/packages/backend/test/resources/kick_gaba7.aac b/packages/backend/test/resources/kick_gaba7.aac
new file mode 100644
index 0000000000..4644542f96
Binary files /dev/null and b/packages/backend/test/resources/kick_gaba7.aac differ
diff --git a/packages/backend/test/resources/kick_gaba7.flac b/packages/backend/test/resources/kick_gaba7.flac
new file mode 100644
index 0000000000..7512812018
Binary files /dev/null and b/packages/backend/test/resources/kick_gaba7.flac differ
diff --git a/packages/backend/test/resources/kick_gaba7.mp3 b/packages/backend/test/resources/kick_gaba7.mp3
new file mode 100644
index 0000000000..6ba317deb1
Binary files /dev/null and b/packages/backend/test/resources/kick_gaba7.mp3 differ
diff --git a/packages/backend/test/resources/kick_gaba7.wav b/packages/backend/test/resources/kick_gaba7.wav
new file mode 100644
index 0000000000..2cd280148e
Binary files /dev/null and b/packages/backend/test/resources/kick_gaba7.wav differ
diff --git a/packages/backend/test/resources/kick_gaba7.webm b/packages/backend/test/resources/kick_gaba7.webm
new file mode 100644
index 0000000000..82c5349cd4
Binary files /dev/null and b/packages/backend/test/resources/kick_gaba7.webm differ
diff --git a/packages/backend/test/unit/FileInfoService.ts b/packages/backend/test/unit/FileInfoService.ts
index d05833560d..f378184c74 100644
--- a/packages/backend/test/unit/FileInfoService.ts
+++ b/packages/backend/test/unit/FileInfoService.ts
@@ -7,10 +7,10 @@ import { ModuleMocker } from 'jest-mock';
 import { Test } from '@nestjs/testing';
 import { GlobalModule } from '@/GlobalModule.js';
 import { FileInfoService } from '@/core/FileInfoService.js';
-import { DI } from '@/di-symbols.js';
+//import { DI } from '@/di-symbols.js';
 import { AiService } from '@/core/AiService.js';
 import type { TestingModule } from '@nestjs/testing';
-import type { jest } from '@jest/globals';
+import { describe, beforeAll, afterAll, test } from '@jest/globals';
 import type { MockFunctionMetadata } from 'jest-mock';
 
 const _filename = fileURLToPath(import.meta.url);
@@ -74,164 +74,271 @@ describe('FileInfoService', () => {
 		});
 	});
 
-	test('Generic JPEG', async () => {
-		const path = `${resources}/Lenna.jpg`;
-		const info = await fileInfoService.getFileInfo(path, { skipSensitiveDetection: true }) as any;
-		delete info.warnings;
-		delete info.blurhash;
-		delete info.sensitive;
-		delete info.porn;
-		assert.deepStrictEqual(info, {
-			size: 25360,
-			md5: '091b3f259662aa31e2ffef4519951168',
-			type: {
-				mime: 'image/jpeg',
-				ext: 'jpg',
-			},
-			width: 512,
-			height: 512,
-			orientation: undefined,
+	describe('IMAGE', () => {
+		test('Generic JPEG', async () => {
+			const path = `${resources}/Lenna.jpg`;
+			const info = await fileInfoService.getFileInfo(path, { skipSensitiveDetection: true }) as any;
+			delete info.warnings;
+			delete info.blurhash;
+			delete info.sensitive;
+			delete info.porn;
+			assert.deepStrictEqual(info, {
+				size: 25360,
+				md5: '091b3f259662aa31e2ffef4519951168',
+				type: {
+					mime: 'image/jpeg',
+					ext: 'jpg',
+				},
+				width: 512,
+				height: 512,
+				orientation: undefined,
+			});
+		});
+	
+		test('Generic APNG', async () => {
+			const path = `${resources}/anime.png`;
+			const info = await fileInfoService.getFileInfo(path, { skipSensitiveDetection: true }) as any;
+			delete info.warnings;
+			delete info.blurhash;
+			delete info.sensitive;
+			delete info.porn;
+			assert.deepStrictEqual(info, {
+				size: 1868,
+				md5: '08189c607bea3b952704676bb3c979e0',
+				type: {
+					mime: 'image/apng',
+					ext: 'apng',
+				},
+				width: 256,
+				height: 256,
+				orientation: undefined,
+			});
+		});
+	
+		test('Generic AGIF', async () => {
+			const path = `${resources}/anime.gif`;
+			const info = await fileInfoService.getFileInfo(path, { skipSensitiveDetection: true }) as any;
+			delete info.warnings;
+			delete info.blurhash;
+			delete info.sensitive;
+			delete info.porn;
+			assert.deepStrictEqual(info, {
+				size: 2248,
+				md5: '32c47a11555675d9267aee1a86571e7e',
+				type: {
+					mime: 'image/gif',
+					ext: 'gif',
+				},
+				width: 256,
+				height: 256,
+				orientation: undefined,
+			});
+		});
+	
+		test('PNG with alpha', async () => {
+			const path = `${resources}/with-alpha.png`;
+			const info = await fileInfoService.getFileInfo(path, { skipSensitiveDetection: true }) as any;
+			delete info.warnings;
+			delete info.blurhash;
+			delete info.sensitive;
+			delete info.porn;
+			assert.deepStrictEqual(info, {
+				size: 3772,
+				md5: 'f73535c3e1e27508885b69b10cf6e991',
+				type: {
+					mime: 'image/png',
+					ext: 'png',
+				},
+				width: 256,
+				height: 256,
+				orientation: undefined,
+			});
+		});
+	
+		test('Generic SVG', async () => {
+			const path = `${resources}/image.svg`;
+			const info = await fileInfoService.getFileInfo(path, { skipSensitiveDetection: true }) as any;
+			delete info.warnings;
+			delete info.blurhash;
+			delete info.sensitive;
+			delete info.porn;
+			assert.deepStrictEqual(info, {
+				size: 505,
+				md5: 'b6f52b4b021e7b92cdd04509c7267965',
+				type: {
+					mime: 'image/svg+xml',
+					ext: 'svg',
+				},
+				width: 256,
+				height: 256,
+				orientation: undefined,
+			});
+		});
+	
+		test('SVG with XML definition', async () => {
+			// https://github.com/misskey-dev/misskey/issues/4413
+			const path = `${resources}/with-xml-def.svg`;
+			const info = await fileInfoService.getFileInfo(path, { skipSensitiveDetection: true }) as any;
+			delete info.warnings;
+			delete info.blurhash;
+			delete info.sensitive;
+			delete info.porn;
+			assert.deepStrictEqual(info, {
+				size: 544,
+				md5: '4b7a346cde9ccbeb267e812567e33397',
+				type: {
+					mime: 'image/svg+xml',
+					ext: 'svg',
+				},
+				width: 256,
+				height: 256,
+				orientation: undefined,
+			});
+		});
+	
+		test('Dimension limit', async () => {
+			const path = `${resources}/25000x25000.png`;
+			const info = await fileInfoService.getFileInfo(path, { skipSensitiveDetection: true }) as any;
+			delete info.warnings;
+			delete info.blurhash;
+			delete info.sensitive;
+			delete info.porn;
+			assert.deepStrictEqual(info, {
+				size: 75933,
+				md5: '268c5dde99e17cf8fe09f1ab3f97df56',
+				type: {
+					mime: 'application/octet-stream',	// do not treat as image
+					ext: null,
+				},
+				width: 25000,
+				height: 25000,
+				orientation: undefined,
+			});
+		});
+	
+		test('Rotate JPEG', async () => {
+			const path = `${resources}/rotate.jpg`;
+			const info = await fileInfoService.getFileInfo(path, { skipSensitiveDetection: true }) as any;
+			delete info.warnings;
+			delete info.blurhash;
+			delete info.sensitive;
+			delete info.porn;
+			assert.deepStrictEqual(info, {
+				size: 12624,
+				md5: '68d5b2d8d1d1acbbce99203e3ec3857e',
+				type: {
+					mime: 'image/jpeg',
+					ext: 'jpg',
+				},
+				width: 512,
+				height: 256,
+				orientation: 8,
+			});
 		});
 	});
 
-	test('Generic APNG', async () => {
-		const path = `${resources}/anime.png`;
-		const info = await fileInfoService.getFileInfo(path, { skipSensitiveDetection: true }) as any;
-		delete info.warnings;
-		delete info.blurhash;
-		delete info.sensitive;
-		delete info.porn;
-		assert.deepStrictEqual(info, {
-			size: 1868,
-			md5: '08189c607bea3b952704676bb3c979e0',
-			type: {
-				mime: 'image/apng',
-				ext: 'apng',
-			},
-			width: 256,
-			height: 256,
-			orientation: undefined,
+	describe('AUDIO', () => {
+		test('MP3', async () => {
+			const path = `${resources}/kick_gaba7.mp3`;
+			const info = await fileInfoService.getFileInfo(path, { skipSensitiveDetection: true }) as any;
+			delete info.warnings;
+			delete info.blurhash;
+			delete info.sensitive;
+			delete info.porn;
+			delete info.width;
+			delete info.height;
+			delete info.orientation;
+			assert.deepStrictEqual(info, {
+				size: 19853,
+				md5: '4f557df8548bc3cecc794c652f690446',
+				type: {
+					mime: 'audio/mpeg',
+					ext: 'mp3',
+				},
+			});
 		});
-	});
-
-	test('Generic AGIF', async () => {
-		const path = `${resources}/anime.gif`;
-		const info = await fileInfoService.getFileInfo(path, { skipSensitiveDetection: true }) as any;
-		delete info.warnings;
-		delete info.blurhash;
-		delete info.sensitive;
-		delete info.porn;
-		assert.deepStrictEqual(info, {
-			size: 2248,
-			md5: '32c47a11555675d9267aee1a86571e7e',
-			type: {
-				mime: 'image/gif',
-				ext: 'gif',
-			},
-			width: 256,
-			height: 256,
-			orientation: undefined,
+	
+		test('WAV', async () => {
+			const path = `${resources}/kick_gaba7.wav`;
+			const info = await fileInfoService.getFileInfo(path, { skipSensitiveDetection: true }) as any;
+			delete info.warnings;
+			delete info.blurhash;
+			delete info.sensitive;
+			delete info.porn;
+			delete info.width;
+			delete info.height;
+			delete info.orientation;
+			assert.deepStrictEqual(info, {
+				size: 87630,
+				md5: '8bc9bb4fe5e77bb1871448209be635c1',
+				type: {
+					mime: 'audio/wav',
+					ext: 'wav',
+				},
+			});
 		});
-	});
-
-	test('PNG with alpha', async () => {
-		const path = `${resources}/with-alpha.png`;
-		const info = await fileInfoService.getFileInfo(path, { skipSensitiveDetection: true }) as any;
-		delete info.warnings;
-		delete info.blurhash;
-		delete info.sensitive;
-		delete info.porn;
-		assert.deepStrictEqual(info, {
-			size: 3772,
-			md5: 'f73535c3e1e27508885b69b10cf6e991',
-			type: {
-				mime: 'image/png',
-				ext: 'png',
-			},
-			width: 256,
-			height: 256,
-			orientation: undefined,
+	
+		test('AAC', async () => {
+			const path = `${resources}/kick_gaba7.aac`;
+			const info = await fileInfoService.getFileInfo(path, { skipSensitiveDetection: true }) as any;
+			delete info.warnings;
+			delete info.blurhash;
+			delete info.sensitive;
+			delete info.porn;
+			delete info.width;
+			delete info.height;
+			delete info.orientation;
+			assert.deepStrictEqual(info, {
+				size: 7291,
+				md5: '2789323f05e3392b648066f50be6a2a6',
+				type: {
+					mime: 'audio/aac',
+					ext: 'aac',
+				},
+			});
 		});
-	});
-
-	test('Generic SVG', async () => {
-		const path = `${resources}/image.svg`;
-		const info = await fileInfoService.getFileInfo(path, { skipSensitiveDetection: true }) as any;
-		delete info.warnings;
-		delete info.blurhash;
-		delete info.sensitive;
-		delete info.porn;
-		assert.deepStrictEqual(info, {
-			size: 505,
-			md5: 'b6f52b4b021e7b92cdd04509c7267965',
-			type: {
-				mime: 'image/svg+xml',
-				ext: 'svg',
-			},
-			width: 256,
-			height: 256,
-			orientation: undefined,
+	
+		test('FLAC', async () => {
+			const path = `${resources}/kick_gaba7.flac`;
+			const info = await fileInfoService.getFileInfo(path, { skipSensitiveDetection: true }) as any;
+			delete info.warnings;
+			delete info.blurhash;
+			delete info.sensitive;
+			delete info.porn;
+			delete info.width;
+			delete info.height;
+			delete info.orientation;
+			assert.deepStrictEqual(info, {
+				size: 108793,
+				md5: 'bc0f3adfe0e1ca99ae6c7528c46b3173',
+				type: {
+					mime: 'audio/flac',
+					ext: 'flac',
+				},
+			});
 		});
-	});
-
-	test('SVG with XML definition', async () => {
-		// https://github.com/misskey-dev/misskey/issues/4413
-		const path = `${resources}/with-xml-def.svg`;
-		const info = await fileInfoService.getFileInfo(path, { skipSensitiveDetection: true }) as any;
-		delete info.warnings;
-		delete info.blurhash;
-		delete info.sensitive;
-		delete info.porn;
-		assert.deepStrictEqual(info, {
-			size: 544,
-			md5: '4b7a346cde9ccbeb267e812567e33397',
-			type: {
-				mime: 'image/svg+xml',
-				ext: 'svg',
-			},
-			width: 256,
-			height: 256,
-			orientation: undefined,
-		});
-	});
-
-	test('Dimension limit', async () => {
-		const path = `${resources}/25000x25000.png`;
-		const info = await fileInfoService.getFileInfo(path, { skipSensitiveDetection: true }) as any;
-		delete info.warnings;
-		delete info.blurhash;
-		delete info.sensitive;
-		delete info.porn;
-		assert.deepStrictEqual(info, {
-			size: 75933,
-			md5: '268c5dde99e17cf8fe09f1ab3f97df56',
-			type: {
-				mime: 'application/octet-stream',	// do not treat as image
-				ext: null,
-			},
-			width: 25000,
-			height: 25000,
-			orientation: undefined,
-		});
-	});
-
-	test('Rotate JPEG', async () => {
-		const path = `${resources}/rotate.jpg`;
-		const info = await fileInfoService.getFileInfo(path, { skipSensitiveDetection: true }) as any;
-		delete info.warnings;
-		delete info.blurhash;
-		delete info.sensitive;
-		delete info.porn;
-		assert.deepStrictEqual(info, {
-			size: 12624,
-			md5: '68d5b2d8d1d1acbbce99203e3ec3857e',
-			type: {
-				mime: 'image/jpeg',
-				ext: 'jpg',
-			},
-			width: 512,
-			height: 256,
-			orientation: 8,
+	
+		/*
+		 * video/webmとして検出されてしまう
+		test('WEBM AUDIO', async () => {
+			const path = `${resources}/kick_gaba7.webm`;
+			const info = await fileInfoService.getFileInfo(path, { skipSensitiveDetection: true }) as any;
+			delete info.warnings;
+			delete info.blurhash;
+			delete info.sensitive;
+			delete info.porn;
+			delete info.width;
+			delete info.height;
+			delete info.orientation;
+			assert.deepStrictEqual(info, {
+				size: 8879,
+				md5: '3350083dec312419cfdc06c16413aca7',
+				type: {
+					mime: 'audio/webm',
+					ext: 'webm',
+				},
+			});
 		});
+		 */
 	});
 });
diff --git a/packages/frontend/src/const.ts b/packages/frontend/src/const.ts
index 1d1b8fcea4..38af9eac9a 100644
--- a/packages/frontend/src/const.ts
+++ b/packages/frontend/src/const.ts
@@ -35,6 +35,11 @@ export const FILE_TYPE_BROWSERSAFE = [
 	'audio/webm',
 
 	'audio/aac',
+
+	// see https://github.com/misskey-dev/misskey/pull/10686
+	'audio/flac',
+	'audio/wav',
+	// backward compatibility
 	'audio/x-flac',
 	'audio/vnd.wave',
 ];