diff --git a/src/client/components/user-moderate-dialog.vue b/src/client/components/user-moderate-dialog.vue
index f45342564..61b8dd0ba 100644
--- a/src/client/components/user-moderate-dialog.vue
+++ b/src/client/components/user-moderate-dialog.vue
@@ -3,7 +3,7 @@
 	<template #header><mk-user-name :user="user"/></template>
 	<div class="vrcsvlkm">
 		<mk-button @click="resetPassword()" primary>{{ $t('resetPassword') }}</mk-button>
-		<mk-switch v-if="$store.state.i.isAdmin" @change="toggleModerator()" v-model="moderator">{{ $t('moderator') }}</mk-switch>
+		<mk-switch v-if="$store.state.i.isAdmin && !user.isAdmin" @change="toggleModerator()" v-model="moderator">{{ $t('moderator') }}</mk-switch>
 		<mk-switch @change="toggleSilence()" v-model="silenced">{{ $t('silence') }}</mk-switch>
 		<mk-switch @change="toggleSuspend()" v-model="suspended">{{ $t('suspend') }}</mk-switch>
 	</div>
@@ -47,7 +47,7 @@ export default Vue.extend({
 				type: 'waiting',
 				iconOnly: true
 			});
-			
+
 			this.$root.api('admin/reset-password', {
 				userId: this.user.id,
 			}).then(({ password }) => {
diff --git a/src/server/api/endpoints/admin/moderators/add.ts b/src/server/api/endpoints/admin/moderators/add.ts
index 71a214928..fd862a9a4 100644
--- a/src/server/api/endpoints/admin/moderators/add.ts
+++ b/src/server/api/endpoints/admin/moderators/add.ts
@@ -32,6 +32,10 @@ export default define(meta, async (ps) => {
 		throw new Error('user not found');
 	}
 
+	if (user.isAdmin) {
+		throw new Error('cannot mark as moderator if admin user');
+	}
+
 	await Users.update(user.id, {
 		isModerator: true
 	});