diff --git a/fitter.py b/fitter.py
index 61a7da6..1ebb17a 100644
--- a/fitter.py
+++ b/fitter.py
@@ -23,7 +23,7 @@ class Fitter:
         self.fit_results = {}
 
         self.tspan = [0, 1000]
-        self.initial_values = self.model.get_initial_values(self)
+        self.initial_values = model.get_initial_values(self)
         self.dt = 1  # 1.0
         self.time_points = np.arange(*self.tspan, self.dt)