diff --git a/README.md b/README.md
index c7c2931..f10dad8 100644
--- a/README.md
+++ b/README.md
@@ -24,7 +24,7 @@ hexshow(h)
 from hexfft import fft, ifft
 
 X = fft(h)
-X_hx = fft(h, periodicity="hex")
+X_hx = fft(h, periodicity="rect") # or "hex"
 ```
 
 #### Operate on a 3D stack