diff --git a/CHANGELOG.md b/CHANGELOG.md
index edd93b07e..b04ee486c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,7 @@
 
 1. [](#bugfix)
     * Improve blueprint initialization in Flex Objects (fixes content aware fields)
+    * Fixed error when activating Flex Accounts in GRAV system configuration (PHP 7.1)
 
 # v1.7.0-beta.8
 ## 09/19/2019
diff --git a/system/src/Grav/Framework/Flex/Traits/FlexMediaTrait.php b/system/src/Grav/Framework/Flex/Traits/FlexMediaTrait.php
index 25e971a72..845aafade 100644
--- a/system/src/Grav/Framework/Flex/Traits/FlexMediaTrait.php
+++ b/system/src/Grav/Framework/Flex/Traits/FlexMediaTrait.php
@@ -346,5 +346,5 @@ trait FlexMediaTrait
 
     abstract public function getFlexDirectory(): FlexDirectory;
 
-    abstract public function getStorageKey();
+    abstract public function getStorageKey(bool $master = false): string;
 }