diff --git a/pointprocesses/lecture/isihexamples.py b/pointprocesses/lecture/isihexamples.py
index 6174e91..7d8d30e 100644
--- a/pointprocesses/lecture/isihexamples.py
+++ b/pointprocesses/lecture/isihexamples.py
@@ -76,7 +76,7 @@ rng = np.random.RandomState(54637281)
 time = np.arange(0.0, duration, dt)
 x = np.zeros(time.shape)+rate
 n = rng.randn(len(time))*drate*tau/np.sqrt(dt)+rate
-for k in np.arange(1,len(x)) :
+for k in range(1,len(x)) :
     x[k] = x[k-1] + (n[k]-x[k-1])*dt/tau
 x[x<0.0] = 0.0