diff --git a/draft-thomson-ppm-prss.md b/draft-thomson-ppm-prss.md
index 3ec031e..41b826c 100644
--- a/draft-thomson-ppm-prss.md
+++ b/draft-thomson-ppm-prss.md
@@ -699,4 +699,4 @@ others to zero.
 # Acknowledgments
 {:numbered="false"}
 
-TODO acknowledge.
+Tim Geoghegan provided constructive feedback.