diff --git a/packages/backend/src/core/AiService.ts b/packages/backend/src/core/AiService.ts
index 248a9b8979..23ab8082ed 100644
--- a/packages/backend/src/core/AiService.ts
+++ b/packages/backend/src/core/AiService.ts
@@ -29,7 +29,7 @@ export class AiService {
 	}
 
 	@bindThis
-	public async detectSensitive(path: string): Promise<nsfw.PredictionType[] | null> {
+	public async detectSensitive(source: string | Buffer): Promise<nsfw.PredictionType[] | null> {
 		try {
 			if (isSupportedCpu === undefined) {
 				isSupportedCpu = await this.computeIsSupportedCpu();
@@ -51,7 +51,7 @@ export class AiService {
 				});
 			}
 
-			const buffer = await fs.promises.readFile(path);
+			const buffer = source instanceof Buffer ? source : await fs.promises.readFile(source);
 			const image = await tf.node.decodeImage(buffer, 3) as any;
 			try {
 				const predictions = await this.model.classify(image);
diff --git a/packages/backend/src/core/FileInfoService.ts b/packages/backend/src/core/FileInfoService.ts
index 6250d4d3a1..62a7d24afb 100644
--- a/packages/backend/src/core/FileInfoService.ts
+++ b/packages/backend/src/core/FileInfoService.ts
@@ -21,6 +21,7 @@ import { LoggerService } from '@/core/LoggerService.js';
 import type Logger from '@/logger.js';
 import { bindThis } from '@/decorators.js';
 import type { PredictionType } from 'nsfwjs';
+import { isMimeImage } from '@/misc/is-mime-image.js';
 
 export type FileInfo = {
 	size: number;
@@ -204,16 +205,7 @@ export class FileInfoService {
 			return [sensitive, porn];
 		}
 
-		if ([
-			'image/jpeg',
-			'image/png',
-			'image/webp',
-		].includes(mime)) {
-			const result = await this.aiService.detectSensitive(source);
-			if (result) {
-				[sensitive, porn] = judgePrediction(result);
-			}
-		} else if (analyzeVideo && (mime === 'image/apng' || mime.startsWith('video/'))) {
+		if (analyzeVideo && (mime === 'image/apng' || mime.startsWith('video/'))) {
 			const [outDir, disposeOutDir] = await createTempDir();
 			try {
 				const command = FFmpeg()
@@ -281,6 +273,23 @@ export class FileInfoService {
 			} finally {
 				disposeOutDir();
 			}
+		} else if (isMimeImage(mime, 'sharp-convertible-image-with-bmp')) {
+			/*
+			 * tfjs-node は限られた画像形式しか受け付けないため、sharp で PNG に変換する
+			 * せっかくなので内部処理で使われる最大サイズの299x299に事前にリサイズする
+			 */
+			const png = await (await sharpBmp(source, mime))
+				.resize(299, 299, {
+					withoutEnlargement: false,
+				})
+				.rotate()
+				.flatten({ background: { r: 119, g: 119, b: 119 } }) // 透過部分を18%グレーで塗りつぶす
+				.png()
+				.toBuffer();
+			const result = await this.aiService.detectSensitive(png);
+			if (result) {
+				[sensitive, porn] = judgePrediction(result);
+			}
 		}
 
 		return [sensitive, porn];