diff --git a/src/SpojeNet/PohodaSQL/Agenda.php b/src/SpojeNet/PohodaSQL/Agenda.php
index 03013e5..f0aeadf 100644
--- a/src/SpojeNet/PohodaSQL/Agenda.php
+++ b/src/SpojeNet/PohodaSQL/Agenda.php
@@ -150,7 +150,7 @@ public function setUp($options = []): bool
      *
      * @return bool Success
      */
-    public function setDataValue($columnName, $value)
+    public function setDataValue(string $columnName, $value): bool
     {
         return \array_key_exists($columnName, $this->struct) ? parent::setDataValue(
             $columnName,