diff --git a/Models/QAAnswer.php b/Models/QAAnswer.php
index 0cdfc59..c13438b 100755
--- a/Models/QAAnswer.php
+++ b/Models/QAAnswer.php
@@ -269,7 +269,7 @@ class QAAnswer implements \JsonSerializable
     /**
      * {@inheritdoc}
      */
-    public function jsonSerialize()
+    public function jsonSerialize() : mixed
     {
         return $this->toArray();
     }
diff --git a/Models/QAApp.php b/Models/QAApp.php
index 03931f2..0075428 100755
--- a/Models/QAApp.php
+++ b/Models/QAApp.php
@@ -66,7 +66,7 @@ class QAApp implements \JsonSerializable
     /**
      * {@inheritdoc}
      */
-    public function jsonSerialize()
+    public function jsonSerialize() : mixed
     {
         return $this->toArray();
     }
diff --git a/Models/QAQuestion.php b/Models/QAQuestion.php
index 61d8af3..386d16b 100755
--- a/Models/QAQuestion.php
+++ b/Models/QAQuestion.php
@@ -491,7 +491,7 @@ class QAQuestion implements \JsonSerializable
     /**
      * {@inheritdoc}
      */
-    public function jsonSerialize()
+    public function jsonSerialize() : mixed
     {
         return $this->toArray();
     }