diff --git a/src/Todo.php b/src/Todo.php
index b5629ac..7516b76 100644
--- a/src/Todo.php
+++ b/src/Todo.php
@@ -5,6 +5,7 @@ namespace MMK2410\MyTodoList;
 class Todo
 {
     const ExceptionMsgInvalidTitle = "Empty task title not allowed";
+    const ExceptionMsgInvalidState = "Invalid state tried to set.";
 
     private string $title;
     private string $state;
@@ -50,7 +51,7 @@ class Todo
         $reflect = new \ReflectionClass(TodoStates::class);
         $constantFound = $reflect->getConstant($state);
         if ($constantFound === FALSE) {
-            throw new \InvalidArgumentException("Invalid state tried to set.");
+            throw new \InvalidArgumentException(self::ExceptionMsgInvalidState);
         }
     }
 }
\ No newline at end of file
diff --git a/tests/TodoTest.php b/tests/TodoTest.php
index e93ff69..1b10605 100644
--- a/tests/TodoTest.php
+++ b/tests/TodoTest.php
@@ -61,7 +61,7 @@ class TodoTest extends TestCase
     {
        $todo = new Todo("stub");
        $this->expectException(\InvalidArgumentException::class);
-       $this->expectExceptionMessage("Invalid state tried to set.");
+       $this->expectExceptionMessage(Todo::ExceptionMsgInvalidState);
        $todo->setState("bogus");
     }
 }