diff --git a/acinclude.m4 b/acinclude.m4
index 77bf110a..5350d315 100644
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -48,8 +48,7 @@ AC_DEFUN([AC_PROG_CC_UBSAN], [
 
 AC_DEFUN([COMPILER_FLAGS], [
 	if (test "${CFLAGS}" = ""); then
-		CFLAGS="-Wall -O2 -fsigned-char -fno-exceptions"
-		CFLAGS+=" -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2"
+		CFLAGS="-Wall -fsigned-char -fno-exceptions"
 	fi
 	if (test "$USE_MAINTAINER_MODE" = "yes"); then
 		CFLAGS+=" -Werror -Wextra"
diff --git a/configure.ac b/configure.ac
index cb576a62..1d10f9df 100644
--- a/configure.ac
+++ b/configure.ac
@@ -37,10 +37,15 @@ LT_INIT([disable-static])
 AC_ARG_ENABLE(optimization, AS_HELP_STRING([--disable-optimization],
 			[disable code optimization through compiler]), [
 	if (test "${enableval}" = "no"); then
-		CFLAGS="$CFLAGS -U_FORTIFY_SOURCE -O0"
+		CFLAGS="$CFLAGS -O0"
 	fi
 ])
 
+if (test "${enable_optimization}" != "no"); then
+	CFLAGS="$CFLAGS -O2"
+	CFLAGS+=" -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2"
+fi
+
 AC_ARG_ENABLE(debug, AS_HELP_STRING([--enable-debug],
 			[enable compiling with debugging information]), [
 	if (test "${enableval}" = "yes" &&