diff --git a/games-emulation/gnuboy/files/gnuboy-1.0.3-fix-implicit-decl-sprintf.patch b/games-emulation/gnuboy/files/gnuboy-1.0.3-fix-implicit-decl-sprintf.patch
new file mode 100644
index 0000000000000..5b4cbfd1cc706
--- /dev/null
+++ b/games-emulation/gnuboy/files/gnuboy-1.0.3-fix-implicit-decl-sprintf.patch
@@ -0,0 +1,25 @@
+From 2c881f1ec456bab7deb4163a2f96814b479a81d7 Mon Sep 17 00:00:00 2001
+From: Sam James <sam@gentoo.org>
+Date: Thu, 19 Aug 2021 01:19:30 +0100
+Subject: [PATCH] Fix implicit declaration of sprintf
+
+--- a/exports.c
++++ b/exports.c
+@@ -1,6 +1,7 @@
+ 
+ 
+ #include <stdlib.h>
++#include <stdio.h>
+ 
+ #include "rc.h"
+ 
+--- a/sys/linux/fbdev.c
++++ b/sys/linux/fbdev.c
+@@ -9,6 +9,7 @@
+ 
+ 
+ #include <stdlib.h>
++#include <stdio.h>
+ #include <string.h>
+ #include <unistd.h>
+ #include <sys/mman.h>
diff --git a/games-emulation/gnuboy/gnuboy-1.0.3-r2.ebuild b/games-emulation/gnuboy/gnuboy-1.0.3-r2.ebuild
index 9a20207a60e7b..90d2531015137 100644
--- a/games-emulation/gnuboy/gnuboy-1.0.3-r2.ebuild
+++ b/games-emulation/gnuboy/gnuboy-1.0.3-r2.ebuild
@@ -12,7 +12,7 @@ SRC_URI="mirror://gentoo/${P}.tar.gz"
 LICENSE="GPL-2"
 SLOT="0"
 KEYWORDS="~amd64 ~x86"
-IUSE="X sdl"
+IUSE="X +sdl"
 REQUIRED_USE="!X? ( sdl )"
 
 RDEPEND="