diff --git a/examples/flopping_f_simulation.py b/examples/flopping_f_simulation.py
index e2b13a349..0248bd6dd 100644
--- a/examples/flopping_f_simulation.py
+++ b/examples/flopping_f_simulation.py
@@ -16,6 +16,13 @@ def model(x, F0):
     return A+(B-A)/2/(4*tpi**2*(x-F0)**2+1)*(1-cos(pi*t/tpi*sqrt(4*tpi**2*(x-F0)**2+1)))
 
 
+def model_numpy(xdata, F0):
+    r = np.zeros(len(xdata))
+    for i, x in enumerate(xdata):
+        r[i] = model(x, F0)
+    return r
+
+
 class FloppingF(AutoDB):
     class DBKeys:
         implicit_core = False
@@ -48,7 +55,7 @@ class FloppingF(AutoDB):
         self.analyze()
 
     def analyze(self):
-        popt, pcov = curve_fit(lambda xdata, F0: [model(x, F0) for x in xdata],
+        popt, pcov = curve_fit(model_numpy,
                                self.frequency.read, self.brightness.read,
                                p0=[self.flopping_freq])
         perr = np.sqrt(np.diag(pcov))