Morlet wavelets have high frequency noise

[mgarrett1955]

I am seeing un unexpected results from the Morlet CWT, mainly high frequency noise in the scaled basis functions:

import numpy as np
import matplotlib.pyplot as plt
import pywt
widths = np.arange(1, 127)
fs = 250
t = 4.0
t = np.zeros(int(fs * t))
t[256] = 1
widths = np.arange(1, 32)
cwt_matrix1, freq = pywt.cwt(t, widths, 'morl', sampling_period=1/fs)
plt.figure(figsize=(15, 5))
plt.plot(cwt_matrix1[24])
plt.show()