diff --git a/core/install.php b/core/install.php
index 6cee3900..ccf8f3a5 100644
--- a/core/install.php
+++ b/core/install.php
@@ -50,7 +50,7 @@ function install(): void
     }
 }
 
-function get_dsn(): string
+function get_dsn(): ?string
 {
     if (getenv("INSTALL_DSN")) {
         $dsn = getenv("INSTALL_DSN");