diff --git a/CONTRIBUTORS.txt b/CONTRIBUTORS.txt
index 38e2ea32..80cb92f0 100644
--- a/CONTRIBUTORS.txt
+++ b/CONTRIBUTORS.txt
@@ -132,6 +132,7 @@
 
 - François Boulogne
   Andres Method for circle perimeter, ellipse perimeter drawing.
+  Hough transform for circles
 
 - Thouis Jones
   Vectorized operators for arrays of 16-bit ints.