diff --git a/mapytex/calculus/core/compute/add.py b/mapytex/calculus/core/compute/add.py
index db0c0be..9a6cc6a 100644
--- a/mapytex/calculus/core/compute/add.py
+++ b/mapytex/calculus/core/compute/add.py
@@ -70,6 +70,9 @@ def monumber_monumber(left, right):
     >>> b = MOnumber(6)
     >>> add(a, b)
     <MOnumber 10>
+    >>> b = MOnumber('2.3')
+    >>> add(a, b)
+    <MOnumber 6.3>
 
     """
     return MO.factory(left.value + right.value)