diff --git a/sci-mathematics/frama-c/frama-c-24.0.ebuild b/sci-mathematics/frama-c/frama-c-24.0.ebuild
index 5234acac61..59f668c96e 100644
--- a/sci-mathematics/frama-c/frama-c-24.0.ebuild
+++ b/sci-mathematics/frama-c/frama-c-24.0.ebuild
@@ -31,6 +31,7 @@ src_prepare() {
 	mv configure.in configure.ac || die
 	sed -i 's/configure\.in/configure.ac/g' Makefile.generating Makefile || die
 	touch config_file || die
+	sed -i '/^\t\$(CC)/s/ -O3 /$(CFLAGS)/' Makefile || die
 	eautoreconf
 	eapply_user
 }