diff --git a/src/includes/constants.php b/src/includes/constants.php
index c408a3457..a6419097c 100644
--- a/src/includes/constants.php
+++ b/src/includes/constants.php
@@ -75,6 +75,13 @@ if (!getenv('SS_IGNORE_DOT_ENV')) {
 
 if (!defined('BASE_URL')) {
     define('BASE_URL', call_user_func(function () {
+        // Prefer explicitly provided SS_BASE_URL
+        $base = getenv('SS_BASE_URL');
+        if ($base) {
+            // Strip relative path from SS_BASE_URL
+            return rtrim(parse_url($base, PHP_URL_PATH), '/');
+        }
+
         // Determine the base URL by comparing SCRIPT_NAME to SCRIPT_FILENAME and getting common elements
         // This tends not to work on CLI
         $path = realpath($_SERVER['SCRIPT_FILENAME']);
@@ -87,13 +94,6 @@ if (!defined('BASE_URL')) {
             }
         }
 
-        // Fall back to SS_BASE_URL
-        $base = getenv('SS_BASE_URL');
-        if ($base) {
-            // Strip relative path from SS_BASE_URL
-            return rtrim(parse_url($base, PHP_URL_PATH), '/');
-        }
-
         // Assume no base_url
         return '';
     }));