diff --git a/rocketpy/simulation/monte_carlo.py b/rocketpy/simulation/monte_carlo.py
index 55dd3d395..b6db1b5b1 100644
--- a/rocketpy/simulation/monte_carlo.py
+++ b/rocketpy/simulation/monte_carlo.py
@@ -1579,7 +1579,8 @@ def time_function_serializer(function_object, t_range=None, sample_time=None):
             t0 = source[0, 0]
             tf = source[-1, 0]
             t = np.arange(t0, tf, sample_time)
-            source = func(t)
+            y = func(t)
+            source = np.column_stack((t, y))
 
         return source