--- a/client.mk
+++ b/client.mk
@@ -86,21 +86,19 @@ endif
 
 ifndef TOPSRCDIR
 ifeq (,$(wildcard client.mk))
 $(error Must run from the client.mk directory, or specify TOPSRCDIR)
 endif
 TOPSRCDIR = $(CWD)
 endif
 
-ifeq (Darwin,$(shell uname -s))
-AUTOCONF ?= autoconf213
-else
-AUTOCONF ?= autoconf-2.13
-endif
+# try to find autoconf 2.13 - discard errors from 'which'
+# MacOS X 10.4 sends "no autoconf*" errors to stdout, discard those via grep
+AUTOCONF ?= $(shell which autoconf-2.13 autoconf2.13 autoconf213 2>/dev/null | grep -v '^no autoconf' | head -1)
 
 MKDIR := mkdir
 SH := /bin/sh
 ifndef MAKE
 MAKE := gmake
 endif
 PERL ?= perl
 PYTHON ?= python