diff --git a/com.woltlab.wcf/package.xml b/com.woltlab.wcf/package.xml
index bbf5922e535..b0598667426 100644
--- a/com.woltlab.wcf/package.xml
+++ b/com.woltlab.wcf/package.xml
@@ -52,6 +52,7 @@
 
 	<!-- 
 	Required order of the following steps for the update to 6.2:
+	<instruction type="script">acp/update_com.woltlab.wcf_6.2_backgroundJob.php</instruction>
 	<instruction type="database" run="standalone">acp/database/update_com.woltlab.wcf_62_step1.php</instruction>
 	<instruction type="script">acp/update_com.woltlab.wcf_6.2_contactOptions.php</instruction>
 	<instruction type="database" run="standalone">acp/database/update_com.woltlab.wcf_62_step2.php</instruction>
diff --git a/wcfsetup/install/files/acp/database/update_com.woltlab.wcf_6.2_step1.php b/wcfsetup/install/files/acp/database/update_com.woltlab.wcf_6.2_step1.php
index 144efaffb35..8fce51d2094 100644
--- a/wcfsetup/install/files/acp/database/update_com.woltlab.wcf_6.2_step1.php
+++ b/wcfsetup/install/files/acp/database/update_com.woltlab.wcf_6.2_step1.php
@@ -10,12 +10,17 @@
 
 use wcf\system\database\table\column\IntDatabaseTableColumn;
 use wcf\system\database\table\column\MediumtextDatabaseTableColumn;
-use wcf\system\database\table\column\TextDatabaseTableColumn;
-use wcf\system\database\table\column\TinyintDatabaseTableColumn;
 use wcf\system\database\table\index\DatabaseTableForeignKey;
+use wcf\system\database\table\index\DatabaseTableIndex;
 use wcf\system\database\table\PartialDatabaseTable;
 
 return [
+    PartialDatabaseTable::create('wcf1_background_job')
+        ->indices([
+            DatabaseTableIndex::create('identifier')
+                ->type(DatabaseTableIndex::UNIQUE_TYPE)
+                ->columns(['identifier']),
+        ]),
     PartialDatabaseTable::create('wcf1_user')
         ->columns([
             IntDatabaseTableColumn::create('avatarFileID')
diff --git a/wcfsetup/install/files/acp/update_com.woltlab.wcf_6.2_backgroundJob.php b/wcfsetup/install/files/acp/update_com.woltlab.wcf_6.2_backgroundJob.php
new file mode 100644
index 00000000000..6c63ba94c92
--- /dev/null
+++ b/wcfsetup/install/files/acp/update_com.woltlab.wcf_6.2_backgroundJob.php
@@ -0,0 +1,21 @@
+<?php
+
+/**
+ * This script removes duplicate background jobs.
+ */
+
+use wcf\system\WCF;
+
+$sql = "DELETE background_jobs
+        FROM   wcf1_background_job background_jobs
+        JOIN   (
+            SELECT   MIN(jobID) as keepID, identifier
+            FROM     wcf1_background_job
+            WHERE    identifier IS NOT NULL
+            GROUP BY identifier
+            HAVING   COUNT(*) > 1
+        ) AS duplicates
+            ON background_jobs.identifier = duplicates.identifier
+        WHERE  background_jobs.jobID <> duplicates.keepID";
+$statement = WCF::getDB()->prepare($sql);
+$statement->execute();
diff --git a/wcfsetup/install/files/lib/system/background/BackgroundQueueHandler.class.php b/wcfsetup/install/files/lib/system/background/BackgroundQueueHandler.class.php
index c9ee141718b..15b2098c640 100644
--- a/wcfsetup/install/files/lib/system/background/BackgroundQueueHandler.class.php
+++ b/wcfsetup/install/files/lib/system/background/BackgroundQueueHandler.class.php
@@ -5,7 +5,6 @@
 use wcf\data\user\User;
 use wcf\system\background\job\AbstractBackgroundJob;
 use wcf\system\background\job\AbstractUniqueBackgroundJob;
-use wcf\system\database\util\PreparedStatementConditionBuilder;
 use wcf\system\exception\ParentClassException;
 use wcf\system\session\SessionHandler;
 use wcf\system\SingletonFactory;
@@ -73,48 +72,17 @@ public function enqueueAt(AbstractBackgroundJob|array $jobs, int $time): void
             $jobs = [$jobs];
         }
 
-        $identifiers = [];
         foreach ($jobs as $job) {
             if (!($job instanceof AbstractBackgroundJob)) {
                 throw new ParentClassException(\get_class($job), AbstractBackgroundJob::class);
             }
-
-            if ($job instanceof AbstractUniqueBackgroundJob) {
-                $identifiers[] = $job->identifier();
-            }
         }
 
-        if ($identifiers !== []) {
-            $conditions = new PreparedStatementConditionBuilder();
-            $conditions->add("identifier IN (?)", [$identifiers]);
-
-            $sql = "SELECT  DISTINCT identifier
-                    FROM    wcf1_background_job
-                    {$conditions}";
-            $statement = WCF::getDB()->prepare($sql);
-            $statement->execute($conditions->getParameters());
-            $existingJobs = $statement->fetchAll(\PDO::FETCH_COLUMN);
-
-            $jobs = \array_filter(
-                $jobs,
-                function ($job) use ($existingJobs) {
-                    if ($job instanceof AbstractUniqueBackgroundJob && \in_array($job->identifier(), $existingJobs)) {
-                        return false;
-                    }
-
-                    return true;
-                }
-            );
-
-            if ($jobs === []) {
-                return;
-            }
-        }
-
-        $sql = "INSERT INTO wcf1_background_job
-                            (job, time, identifier)
-                VALUES      (?, ?, ?)";
+        $sql = "INSERT IGNORE INTO wcf1_background_job
+                                   (job, time, identifier)
+                VALUES             (?, ?, ?)";
         $statement = WCF::getDB()->prepare($sql);
+
         foreach ($jobs as $job) {
             $identifier = null;
             if ($job instanceof AbstractUniqueBackgroundJob) {
diff --git a/wcfsetup/setup/db/install.sql b/wcfsetup/setup/db/install.sql
index 185ebbf105a..3872d826f2e 100644
--- a/wcfsetup/setup/db/install.sql
+++ b/wcfsetup/setup/db/install.sql
@@ -241,7 +241,7 @@ CREATE TABLE wcf1_background_job (
 	time INT(10) NOT NULL,
 	identifier VARCHAR(191) NULL,
 
-	KEY identifier (identifier),
+	UNIQUE KEY identifier (identifier),
 	KEY (status, time)
 );