diff --git a/sys-devel/dev86/dev86-0.16.21-r3.ebuild b/sys-devel/dev86/dev86-0.16.21-r3.ebuild
index 9ebecb55cb3d6..e5f0660f954f7 100644
--- a/sys-devel/dev86/dev86-0.16.21-r3.ebuild
+++ b/sys-devel/dev86/dev86-0.16.21-r3.ebuild
@@ -37,10 +37,11 @@ src_prepare() {
 			makefile.in || die
 	fi
 
-	sed -i -e "s|-O2 -g|${CFLAGS}|" -e '/INEXE=/s:-s::' makefile.in || die
+	sed -i -e "s|-O2 -g|${CFLAGS} -std=gnu89|" -e '/INEXE=/s:-s::' makefile.in || die
 	sed -i -e "s:/lib/:/$(get_libdir)/:" bcc/bcc.c || die
 	sed -i -e '/INSTALL_OPTS=/s:-s::' bin86/Makefile || die
 	sed -i -e '/install -m 755 -s/s:-s::' dis88/Makefile || die
+	sed -i -e 's:CFLAGS=-O:CFLAGS=-O -std=gnu89:' dis88/Makefile || die
 }
 
 src_compile() {
@@ -63,7 +64,7 @@ src_compile() {
 
 	cd bootblocks || die
 	emake \
-		HOSTCC="$(tc-getCC)"
+		HOSTCC="$(tc-getCC) -std=gnu89"
 
 }