diff --git a/package.json b/package.json
index 1f7d570f56..093f0d99c6 100644
--- a/package.json
+++ b/package.json
@@ -153,7 +153,6 @@
 		"http-signature": "1.3.5",
 		"idb-keyval": "5.1.3",
 		"insert-text-at-cursor": "0.3.0",
-		"is-root": "2.1.0",
 		"is-svg": "4.3.1",
 		"js-yaml": "4.1.0",
 		"jsdom": "16.7.0",
diff --git a/src/@types/is-root.d.ts b/src/@types/is-root.d.ts
deleted file mode 100644
index 3905a16c8d..0000000000
--- a/src/@types/is-root.d.ts
+++ /dev/null
@@ -1,7 +0,0 @@
-declare module 'is-root' {
-	function isRoot(): boolean;
-
-	namespace isRoot {} // Hack
-
-	export = isRoot;
-}
diff --git a/src/boot/master.ts b/src/boot/master.ts
index 473e215bac..3d86a5dab8 100644
--- a/src/boot/master.ts
+++ b/src/boot/master.ts
@@ -2,7 +2,6 @@ import * as os from 'os';
 import * as cluster from 'cluster';
 import * as chalk from 'chalk';
 import * as portscanner from 'portscanner';
-import * as isRoot from 'is-root';
 import { getConnection } from 'typeorm';
 
 import Logger from '../services/logger';
@@ -39,6 +38,11 @@ function greet() {
 	bootLogger.info(`Misskey v${meta.version}`, null, true);
 }
 
+function isRoot() {
+	// maybe process.getuid will be undefined under not POSIX environment (e.g. Windows)
+	return process.getuid != null && process.getuid() === 0;
+}
+
 /**
  * Init master process
  */
diff --git a/yarn.lock b/yarn.lock
index ecb0ff9739..13e906a261 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -6383,11 +6383,6 @@ is-resolvable@^1.1.0:
   resolved "https://registry.yarnpkg.com/is-resolvable/-/is-resolvable-1.1.0.tgz#fb18f87ce1feb925169c9a407c19318a3206ed88"
   integrity sha512-qgDYXFSR5WvEfuS5dMj6oTMEbrrSaM0CrFk2Yiq/gXnBvD9pMa2jGXxyhGLfvhZpuMZe18CJpFxAt3CRs42NMg==
 
-is-root@2.1.0:
-  version "2.1.0"
-  resolved "https://registry.yarnpkg.com/is-root/-/is-root-2.1.0.tgz#809e18129cf1129644302a4f8544035d51984a9c"
-  integrity sha512-AGOriNp96vNBd3HtU+RzFEc75FfR5ymiYv8E553I71SCeXBiMsVDUtdio1OEFvrPyLIQ9tVR5RxXIFe5PUFjMg==
-
 is-stream@^2.0.0:
   version "2.0.0"
   resolved "https://registry.yarnpkg.com/is-stream/-/is-stream-2.0.0.tgz#bde9c32680d6fae04129d6ac9d921ce7815f78e3"