diff --git a/build/autogen.sh b/build/autogen.sh
index e35d2ee..cf9b75a 100755
--- a/build/autogen.sh
+++ b/build/autogen.sh
@@ -5,7 +5,7 @@ set -e
 
 rm -rf autom4te*.cache
 
-grep AC_CONFIG_HEADER configure.in >/dev/null && autoheader
+grep AC_CONFIG_HEADER configure.ac >/dev/null && autoheader
 autoconf
 
 rm -rf autom4te*.cache
diff --git a/configure.in b/configure.ac
similarity index 85%
rename from configure.in
rename to configure.ac
index d28211e..3af0f1e 100644
--- a/configure.in
+++ b/configure.ac
@@ -1,9 +1,9 @@
 ## smbldap-tools configure.in
 ## ======================================================================
 
-AC_PREREQ(2.50)
+AC_PREREQ([2.71])
 
-AC_INIT(smbldap-tools, 0.9.11)
+AC_INIT([smbldap-tools],[0.9.11])
 
 AC_PREFIX_DEFAULT(/usr/local)
 
@@ -30,8 +30,7 @@ AC_SUBST(package_subdir)
 
 AC_ARG_WITH(
   subdir,
-  [AC_HELP_STRING(--with-subdir=DIR,
-    [change default subdirectory used for installs])],
+  [AS_HELP_STRING([--with-subdir=DIR],[change default subdirectory used for installs])],
   [package_subdir="$withval"],
 )
 
@@ -52,7 +51,7 @@ AC_SUBST(PERL_COMMAND)
 
 AC_ARG_WITH(
     perl,
-    [AC_HELP_STRING(--with-perl=PATH, [Use specific perl command])],
+    [AS_HELP_STRING([--with-perl=PATH],[Use specific perl command])],
     [PERL_COMMAND="$withval"],
 )
 
@@ -95,7 +94,7 @@ AC_SUBST(PERL_LIBDIR)
 
 AC_ARG_WITH(
     perl-libdir,
-    [AC_HELP_STRING(--with-perl-libdir=PATH,[*.pm install directory])],
+    [AS_HELP_STRING([--with-perl-libdir=PATH],[*.pm install directory])],
     [PERL_LIBDIR="$withval"],
 )
 
@@ -118,7 +117,7 @@ AC_SUBST(POD2MAN_COMMAND)
 
 AC_ARG_WITH(
     pod2man,
-    [AC_HELP_STRING(--with-pod2man=PATH, [Use specific pod2man command])],
+    [AS_HELP_STRING([--with-pod2man=PATH],[Use specific pod2man command])],
     [POD2MAN_COMMAND="$withval"],
 )
 
@@ -139,8 +138,7 @@ AC_SUBST(SAMBA_SYSCONFDIR)
 
 AC_ARG_WITH(
     samba-sysconfdir,
-    [AC_HELP_STRING(--with-samba-sysconfdir=DIR,
-	[Path for Samba sysconf directory])],
+    [AS_HELP_STRING([--with-samba-sysconfdir=DIR],[Path for Samba sysconf directory])],
     [SAMBA_SYSCONFDIR="$withval"],
 )
 
@@ -152,8 +150,7 @@ AC_SUBST(SAMBA_BINDIR)
 
 AC_ARG_WITH(
     samba_bindir,
-    [AC_HELP_STRING([--with-samba-bindir=DIR],
-	[Path for Samba bin directory])],
+    [AS_HELP_STRING([--with-samba-bindir=DIR],[Path for Samba bin directory])],
     [SAMBA_BINDIR="$withval"],
 )