diff --git a/configure.ac b/configure.ac
index 34aa6e9be..9105a43b0 100644
--- a/configure.ac
+++ b/configure.ac
@@ -26,7 +26,7 @@ Boston, MA 02110-1301, USA.
 
 ]])
 
-AC_PREREQ(2.61)
+AC_PREREQ([2.71])
 
 dnl  `patsubst' here deletes the newline which "echo" prints.  We can't use
 dnl  "echo -n" since -n is not portable (see autoconf manual "Limitations of
diff --git a/guile-readline/configure.ac b/guile-readline/configure.ac
index fd49cfd65..fdf9518b6 100644
--- a/guile-readline/configure.ac
+++ b/guile-readline/configure.ac
@@ -1,4 +1,4 @@
-AC_PREREQ(2.50)
+AC_PREREQ([2.71])
 
 dnl Don't use "echo -n", which is not portable (e.g., not available on
 dnl MacOS X).  Instead, use `patsubst' to remove the newline.