diff --git a/configure.in b/configure.in
index 23abe117..c300d6a3 100644
--- a/configure.in
+++ b/configure.in
@@ -2,6 +2,9 @@ dnl Process this file with autoconf to produce a configure script.
 AC_INIT(byteorder.h)
 AC_CONFIG_HEADER(config.h)
 
+# compile with optimisation and without debugging by default
+CFLAGS=${CFLAGS-"-O"}
+
 AC_CANONICAL_SYSTEM
 AC_VALIDATE_CACHE_SYSTEM_TYPE