diff --git a/tests/Fixtures/Identifiable.php b/tests/Fixtures/Identifiable.php
index e2d498f..2c8100c 100644
--- a/tests/Fixtures/Identifiable.php
+++ b/tests/Fixtures/Identifiable.php
@@ -44,7 +44,7 @@ class Identifiable implements InstanceIdentifier
      *
      * @return int|string
      */
-    public function getInstanceGlobalDiscount()
+    public function getInstanceGlobalDiscount(): float
     {
         return $this->discountRate;
     }