diff --git a/arch/um/include/shared/os.h b/arch/um/include/shared/os.h
index f06a5da..83c7c2e 100644
--- a/arch/um/include/shared/os.h
+++ b/arch/um/include/shared/os.h
@@ -244,6 +244,7 @@
 extern void setup_machinename(char *machine_out);
 extern void setup_hostinfo(char *buf, int len);
 extern void os_dump_core(void) __attribute__ ((noreturn));
+extern void um_early_printk(const char *s, unsigned int n);
 
 /* time.c */
 extern void idle_sleep(unsigned long long nsecs);