diff --git a/srcpkgs/gcc/template b/srcpkgs/gcc/template
index 758019a545a..561dc9d6ea3 100644
--- a/srcpkgs/gcc/template
+++ b/srcpkgs/gcc/template
@@ -61,7 +61,8 @@ pre_configure() {
 	case "$XBPS_TARGET_MACHINE" in
 		*-musl) patch -Np1 -i ${FILESDIR}/gcc-${version}-musl.diff;;
 	esac
-
+	# _FORTIFY_SOURCE needs an optimization level.
+	sed -i "/ac_cpp=/s/\$CPPFLAGS/\$CPPFLAGS -O2/" {gcc,libiberty}/configure
 	# As specified in the LFS book, disable installing libiberty.
 	sed -i 's/install_to_$(INSTALL_DEST) //' libiberty/Makefile.in
 	# Do not run fixincludes