diff --git a/configure.ac b/configure.ac
index d7d506e..41f0890 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1,6 +1,9 @@
 
 # Initialize Autoconf
-AC_PREREQ([2.70])
+# conda-forge patch: upstream requires Autoconf 2.70, but our Windows tooling
+# only provides 2.69 and is difficult to update. But it appears that we can
+# get away with 2.69, so:
+AC_PREREQ([2.69])
 AC_INIT([libX11], [1.8.7],
         [https://gitlab.freedesktop.org/xorg/lib/libx11/-/issues], [libX11])
 AC_CONFIG_SRCDIR([Makefile.am])