diff --git a/build/lib/multislice/prop_utils.py b/build/lib/multislice/prop_utils.py
index 6e2833f..5b4e537 100644
--- a/build/lib/multislice/prop_utils.py
+++ b/build/lib/multislice/prop_utils.py
@@ -59,10 +59,10 @@ def modify(wavefront,zp_delta,zp_beta,step_z,wavel):
     beta_slice = zp_beta
     delta_slice = zp_delta
     '''
-    Perform the following with numexpr
+    Compute the following with numexpr
     wavefront * np.exp((kz * delta_slice) * 1j) * np.exp(-kz * beta_slice)
     '''
-    return ne.evaluate('wavefront*exp((kz*delta_slice)*1j  - (kz*beta_slice))')
+    return ne.evaluate('wavefront*exp(kz*(delta_slice*1j - beta_slice))')
 
 
 
diff --git a/dist/multislice-0.0.0-py3.6.egg b/dist/multislice-0.0.0-py3.6.egg
index 56d7cb0..5828885 100644
Binary files a/dist/multislice-0.0.0-py3.6.egg and b/dist/multislice-0.0.0-py3.6.egg differ