diff --git a/configure.ac b/configure.ac
index f0629038..c3e91fb6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -8,6 +8,7 @@ AC_CONFIG_HEADERS(config.h)
 AC_PROG_CXX
 AC_PROG_LIBTOOL
 
+RAK_CHECK_CXXFLAGS
 RAK_ENABLE_DEBUG
 RAK_ENABLE_EXTRA_DEBUG
 RAK_ENABLE_WERROR
diff --git a/scripts/rak_compiler.m4 b/scripts/rak_compiler.m4
index 39bd19a7..87871abf 100644
--- a/scripts/rak_compiler.m4
+++ b/scripts/rak_compiler.m4
@@ -1,3 +1,16 @@
+AC_DEFUN([RAK_CHECK_CXXFLAGS], [
+
+  AC_MSG_CHECKING([for user-defined CXXFLAGS])
+
+  if test -n "$CXXFLAGS"; then
+    AC_MSG_RESULT([user-defined "$CXXFLAGS"])
+  else
+    CXXFLAGS="-O2"
+    AC_MSG_RESULT([default "$CXXFLAGS"])
+  fi
+])
+
+
 AC_DEFUN([RAK_ENABLE_DEBUG], [
   AC_ARG_ENABLE(debug,
     AC_HELP_STRING([--enable-debug], [enable debug information [[default=yes]]]),