diff -uNr qemu-4.2.0/tcg/i386/tcg-target.inc.c qemu-4.2.0.mod/tcg/i386/tcg-target.inc.c
--- qemu-4.2.0/tcg/i386/tcg-target.inc.c	2019-12-12 20:20:48.000000000 +0200
+++ qemu-4.2.0.mod/tcg/i386/tcg-target.inc.c	2019-12-15 00:06:29.506302636 +0200
@@ -1968,7 +1968,12 @@
 # if defined(__x86_64__) && defined(__linux__)
 #  include <asm/prctl.h>
 #  include <sys/prctl.h>
-int arch_prctl(int code, unsigned long addr);
+#  include <linux/unistd.h>
+static int arch_prctl(int code, unsigned long addr)
+{
+    return syscall(__NR_arch_prctl, code, addr);
+}
+
 static inline int setup_guest_base_seg(void)
 {
     if (arch_prctl(ARCH_SET_GS, guest_base) == 0) {