diff --git a/libctf/configure.ac b/libctf/configure.ac
index ced1aeb7ccf..51ad76e9755 100644
--- a/libctf/configure.ac
+++ b/libctf/configure.ac
@@ -18,7 +18,7 @@ dnl along with this program; see the file COPYING.  If not see
 dnl <http://www.gnu.org/licenses/>.
 dnl
 
-AC_PREREQ(2.64)
+AC_PREREQ([2.64])
 AC_INIT([libctf], 1.2.0)
 AC_CONFIG_SRCDIR(ctf-impl.h)
 AC_CANONICAL_BUILD
diff --git a/readline/readline/configure.ac b/readline/readline/configure.ac
index 9ea2a6b4b5e..6a9d77f0c51 100644
--- a/readline/readline/configure.ac
+++ b/readline/readline/configure.ac
@@ -27,7 +27,7 @@ m4_include([../../config/override.m4])
 AC_INIT(readline, 8.1, bug-readline@gnu.org)
 
 dnl make sure we are using a recent autoconf version
-AC_PREREQ(2.50)
+AC_PREREQ([2.50])
 
 AC_CONFIG_SRCDIR(readline.h)
 dnl GDB LOCAL