diff --git a/packages/backend/package.json b/packages/backend/package.json
index eccba10ed..f2fe009a9 100644
--- a/packages/backend/package.json
+++ b/packages/backend/package.json
@@ -31,8 +31,6 @@
 		"@peertube/http-signature": "1.7.0",
 		"@sinonjs/fake-timers": "9.1.2",
 		"@syuilo/aiscript": "0.11.1",
-		"@types/pg": "8.6.5",
-		"@types/unzipper": "0.10.5",
 		"ajv": "8.11.0",
 		"archiver": "5.3.1",
 		"autobind-decorator": "2.4.0",
@@ -133,6 +131,7 @@
 		"@redocly/openapi-core": "1.0.0-beta.108",
 		"@swc/core": "1.3.2",
 		"@swc/jest": "0.2.22",
+		"@types/archiver": "5.3.1",
 		"@types/bcryptjs": "2.4.2",
 		"@types/bull": "3.15.9",
 		"@types/cbor": "6.0.0",
@@ -154,10 +153,12 @@
 		"@types/koa__cors": "3.1.1",
 		"@types/koa__multer": "2.0.4",
 		"@types/koa__router": "8.0.11",
+		"@types/mime-types": "2.1.1",
 		"@types/node": "18.7.18",
 		"@types/node-fetch": "3.0.3",
 		"@types/nodemailer": "6.4.6",
 		"@types/oauth": "0.9.1",
+		"@types/pg": "8.6.5",
 		"@types/pug": "2.0.6",
 		"@types/punycode": "2.1.0",
 		"@types/qrcode": "1.5.0",
@@ -172,6 +173,7 @@
 		"@types/speakeasy": "2.0.7",
 		"@types/tinycolor2": "1.4.3",
 		"@types/tmp": "0.2.3",
+		"@types/unzipper": "0.10.5",
 		"@types/uuid": "8.3.4",
 		"@types/web-push": "3.3.2",
 		"@types/websocket": "1.0.5",
diff --git a/packages/backend/src/queue/processors/ExportCustomEmojisProcessorService.ts b/packages/backend/src/queue/processors/ExportCustomEmojisProcessorService.ts
index aa7a0ef92..f8f261b47 100644
--- a/packages/backend/src/queue/processors/ExportCustomEmojisProcessorService.ts
+++ b/packages/backend/src/queue/processors/ExportCustomEmojisProcessorService.ts
@@ -80,7 +80,7 @@ export class ExportCustomEmojisProcessorService {
 		});
 
 		for (const emoji of customEmojis) {
-			const ext = mime.extension(emoji.type);
+			const ext = mime.extension(emoji.type ?? 'image/png');
 			const fileName = emoji.name + (ext ? '.' + ext : '');
 			const emojiPath = path + '/' + fileName;
 			fs.writeFileSync(emojiPath, '', 'binary');
diff --git a/packages/backend/yarn.lock b/packages/backend/yarn.lock
index f2ea0b0a5..598451fa8 100644
--- a/packages/backend/yarn.lock
+++ b/packages/backend/yarn.lock
@@ -1215,6 +1215,13 @@
   dependencies:
     "@types/node" "*"
 
+"@types/archiver@5.3.1":
+  version "5.3.1"
+  resolved "https://registry.yarnpkg.com/@types/archiver/-/archiver-5.3.1.tgz#02991e940a03dd1a32678fead4b4ca03d0e387ca"
+  integrity sha512-wKYZaSXaDvTZuInAWjCeGG7BEAgTWG2zZW0/f7IYFcoHB2X2d9lkVFnrOlXl3W6NrvO6Ml3FLLu8Uksyymcpnw==
+  dependencies:
+    "@types/glob" "*"
+
 "@types/babel__core@^7.1.14":
   version "7.1.19"
   resolved "https://registry.yarnpkg.com/@types/babel__core/-/babel__core-7.1.19.tgz#7b497495b7d1b4812bdb9d02804d0576f43ee460"
@@ -1348,6 +1355,14 @@
   dependencies:
     "@types/node" "*"
 
+"@types/glob@*":
+  version "8.0.0"
+  resolved "https://registry.yarnpkg.com/@types/glob/-/glob-8.0.0.tgz#321607e9cbaec54f687a0792b2d1d370739455d2"
+  integrity sha512-l6NQsDDyQUVeoTynNpC9uRvCUint/gSUXQA2euwmTuWGvPY5LSDUu6tkCtJB2SvGQlJQzLaKqcGZP4//7EDveA==
+  dependencies:
+    "@types/minimatch" "*"
+    "@types/node" "*"
+
 "@types/graceful-fs@^4.1.3":
   version "4.1.5"
   resolved "https://registry.yarnpkg.com/@types/graceful-fs/-/graceful-fs-4.1.5.tgz#21ffba0d98da4350db64891f92a9e5db3cdb4e15"
@@ -1565,11 +1580,21 @@
   resolved "https://registry.yarnpkg.com/@types/long/-/long-4.0.2.tgz#b74129719fc8d11c01868010082d483b7545591a"
   integrity sha512-MqTGEo5bj5t157U6fA/BiDynNkn0YknVdh48CMPkTSpFTVmvao5UQmm7uEF6xBEo7qIMAlY/JSleYaE6VOdpaA==
 
+"@types/mime-types@2.1.1":
+  version "2.1.1"
+  resolved "https://registry.yarnpkg.com/@types/mime-types/-/mime-types-2.1.1.tgz#d9ba43490fa3a3df958759adf69396c3532cf2c1"
+  integrity sha512-vXOTGVSLR2jMw440moWTC7H19iUyLtP3Z1YTj7cSsubOICinjMxFeb/V57v9QdyyPGbbWolUFSSmSiRSn94tFw==
+
 "@types/mime@*":
   version "2.0.1"
   resolved "https://registry.yarnpkg.com/@types/mime/-/mime-2.0.1.tgz#dc488842312a7f075149312905b5e3c0b054c79d"
   integrity sha512-FwI9gX75FgVBJ7ywgnq/P7tw+/o1GUbtP0KzbtusLigAOgIgNISRK0ZPl4qertvXSIE8YbsVJueQ90cDt9YYyw==
 
+"@types/minimatch@*":
+  version "5.1.2"
+  resolved "https://registry.yarnpkg.com/@types/minimatch/-/minimatch-5.1.2.tgz#07508b45797cb81ec3f273011b054cd0755eddca"
+  integrity sha512-K0VQKziLUWkVKiRVrx4a40iPaxTUefQmjtkQofBkYRcoaaL/8rhwDWww9qWbrgicNOgnpIsMxyNIUM4+n6dUIA==
+
 "@types/node-fetch@3.0.3":
   version "3.0.3"
   resolved "https://registry.yarnpkg.com/@types/node-fetch/-/node-fetch-3.0.3.tgz#9d969c9a748e841554a40ee435d26e53fa3ee899"