diff --git a/Sources/Config.php b/Sources/Config.php
index f9f542e683..a2f347f13b 100644
--- a/Sources/Config.php
+++ b/Sources/Config.php
@@ -249,11 +249,15 @@ class Config
 
 	######### Modification Support #########
 	/**
-	 * @var bool
+	 * @var int
 	 *
-	 * Master switch to enable backward compatibility behaviours.
+	 * Master switch to enable backward compatibility behaviours:
+	 * 0: Off. This is the default.
+	 * 1: On. This will be set automatically if an installed modification needs it.
+	 * 2: Forced on. Use this to enable backward compatibility behaviours even when
+	 *    no installed modifications require them. This is usually not necessary.
 	 */
-	public static bool $backward_compatibility = true;
+	public static int $backward_compatibility;
 
 	######### Legacy settings #########
 	/**
@@ -783,13 +787,17 @@ class Config
 
 				######### Modification Support #########
 				/**
-				 * @var bool
+				 * @var int
 				 *
-				 * Master switch to enable backward compatibility behaviours.
+				 * Master switch to enable backward compatibility behaviours:
+				 * 0: Off. This is the default.
+				 * 1: On. This will be set automatically if an installed modification needs it.
+				 * 2: Forced on. Use this to enable backward compatibility behaviours even when
+				 *    no installed modifications require them. This is usually not necessary.
 				 */
 				END,
-			'default' => true,
-			'type' => 'boolean',
+			'default' => 0,
+			'type' => 'integer',
 		],
 		'db_character_set' => [
 			'text' => <<<'END'
@@ -956,7 +964,7 @@ public static function set(array $settings): void
 
 		// For backward compatibility, make settings available as global variables.
 		// Must do this manually because SMF\BackwardCompatibility is not loaded yet.
-		if (self::$backward_compatibility && !self::$exported) {
+		if (!empty(self::$backward_compatibility) && !self::$exported) {
 			foreach ($settings as $var => $val) {
 				if (property_exists(__CLASS__, $var)) {
 					$GLOBALS[$var] = &self::${$var};
diff --git a/Sources/PackageManager/PackageManager.php b/Sources/PackageManager/PackageManager.php
index 72e29f1e94..7dc26f85d1 100644
--- a/Sources/PackageManager/PackageManager.php
+++ b/Sources/PackageManager/PackageManager.php
@@ -1412,6 +1412,50 @@ public function install(): void
 
 		// Restore file permissions?
 		SubsPackage::create_chmod_control([], [], true);
+
+		// Does Config::$backward_compatibility need to be updated?
+		$this->updateBackwardCompatibility();
+	}
+
+	/**
+	 * Enables Config::$backward_compatibility if it is needed.
+	 *
+	 * Once support for backward compatibility behaviours has been discontinued
+	 * in a future version of SMF, this method can be removed.
+	 */
+	public function updateBackwardCompatibility(): void
+	{
+		// If it has been forced on, leave it alone.
+		if ((Config::$backward_compatibility ?? null) === 2) {
+			return;
+		}
+
+		$min_version = preg_replace('/^(\d+\.\d+).*/', '$1.dev.0', SMF_VERSION);
+
+		$request = Db::$db->query(
+			'',
+			'SELECT smf_version
+			FROM {db_prefix}log_packages
+			WHERE install_state != {int:not_installed}
+			ORDER BY smf_version ASC',
+			[
+				'not_installed' => 0,
+			],
+		);
+
+		while ($row = Db::$db->fetch_assoc($request)) {
+			$row['smf_version'] = strtr(strtolower($row['smf_version']), ' ', '.');
+
+			if (version_compare($row['smf_version'], $min_version, '<')) {
+				break;
+			}
+		}
+
+		Db::$db->free_result($request);
+
+		Config::updateSettingsFile([
+			'backward_compatibility' => version_compare($row['smf_version'], $min_version, '<'),
+		]);
 	}
 
 	/**
diff --git a/other/Settings.php b/other/Settings.php
index d5557aeffe..3b7e0ccae6 100644
--- a/other/Settings.php
+++ b/other/Settings.php
@@ -224,11 +224,15 @@
 
 ######### Modification Support #########
 /**
- * @var bool
+ * @var int
  *
- * Master switch to enable backward compatibility behaviours.
+ * Master switch to enable backward compatibility behaviours:
+ * 0: Off. This is the default.
+ * 1: On. This will be set automatically if an installed modification needs it.
+ * 2: Forced on. Use this to enable backward compatibility behaviours even when
+ *    no installed modifications require them. This is usually not necessary.
  */
-$backward_compatibility = true;
+$backward_compatibility = 0;
 
 ######### Legacy Settings #########
 /**
diff --git a/other/Settings_bak.php b/other/Settings_bak.php
index d5557aeffe..3b7e0ccae6 100644
--- a/other/Settings_bak.php
+++ b/other/Settings_bak.php
@@ -224,11 +224,15 @@
 
 ######### Modification Support #########
 /**
- * @var bool
+ * @var int
  *
- * Master switch to enable backward compatibility behaviours.
+ * Master switch to enable backward compatibility behaviours:
+ * 0: Off. This is the default.
+ * 1: On. This will be set automatically if an installed modification needs it.
+ * 2: Forced on. Use this to enable backward compatibility behaviours even when
+ *    no installed modifications require them. This is usually not necessary.
  */
-$backward_compatibility = true;
+$backward_compatibility = 0;
 
 ######### Legacy Settings #########
 /**