Index: configure.ac
==================================================================
--- configure.ac
+++ configure.ac
@@ -1,7 +1,11 @@
 AC_INIT(ObjFW, 0.8-dev, js@webkeks.org)
 BUILDSYS_INIT
+
+AS_IF([test configure.ac -nt configure], [
+	AC_MSG_ERROR([configure.ac is newer than configure! Run ./autogen.sh!])
+])
 
 AC_CONFIG_SRCDIR(src)
 
 AC_CANONICAL_HOST