Add entry to ACKS.
diff --git a/Doc/ACKS.txt b/Doc/ACKS.txt
index f695403..fcbdad7 100644
--- a/Doc/ACKS.txt
+++ b/Doc/ACKS.txt
@@ -103,6 +103,7 @@
 * Detlef Lannert
 * Piers Lauder
 * Glyph Lefkowitz
+* Robert Lehmann
 * Marc-André Lemburg
 * Ulf A. Lindgren
 * Everett Lipman