incompatibility when multiplying a unit by a numpy.float64

This code:
import numpy as np
import scimath
from scimath.units.time import second

print 'version = ',scimath.**version**

t = 3.0 \* second
k = 1.0 / second

print 4 \* t
print t \* np.exp(-k*t)

gives this error:
version = 4.1.0
12.0_s
Traceback (most recent call last):
File "C:\users\jkitchin\Dropbox.spyder2.temp.py", line 19, in
print t \* np.exp(-k_t)
File "C:\Python27\lib\site-packages\scimath\units\unit.py", line 78, in **mul**
value = self.value \* other.value
AttributeError: 'numpy.float64' object has no attribute 'value'

the problem seems to be the return value from the np.exp is missing the value attribute.

this works fine:
print t \* float(np.exp(-k*t))