diff --git a/arch/s390/boot/boot.h b/arch/s390/boot/boot.h
index 80e86387bee5..dbfba6822d6f 100644
--- a/arch/s390/boot/boot.h
+++ b/arch/s390/boot/boot.h
@@ -72,7 +72,7 @@ void print_pgm_check_info(void);
 unsigned long randomize_within_range(unsigned long size, unsigned long align,
 				     unsigned long min, unsigned long max);
 void setup_vmem(unsigned long kernel_start, unsigned long kernel_end, unsigned long asce_limit);
-void __printf(1, 2) boot_printk(const char *fmt, ...);
+int __printf(1, 2) boot_printk(const char *fmt, ...);
 void print_stacktrace(unsigned long sp);
 void error(char *m);
 int get_random(unsigned long limit, unsigned long *value);
diff --git a/arch/s390/boot/printk.c b/arch/s390/boot/printk.c
index e49a9be6d555..311fb45c097c 100644
--- a/arch/s390/boot/printk.c
+++ b/arch/s390/boot/printk.c
@@ -174,7 +174,7 @@ static void boot_console_earlyprintk(const char *buf)
 	 (lenmod == 'z') ? va_arg(args, typemod long) :			\
 			   va_arg(args, typemod int))
 
-void boot_printk(const char *fmt, ...)
+int boot_printk(const char *fmt, ...)
 {
 	char buf[1024] = { 0 };
 	char *end = buf + sizeof(buf) - 1; /* make sure buf is 0 terminated */
@@ -248,4 +248,5 @@ void boot_printk(const char *fmt, ...)
 		boot_rb_add(buf, len);
 		boot_console_earlyprintk(buf);
 	}
+	return len;
 }