diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 09d5b8143b94..eab6a64517c3 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -837,7 +837,12 @@ static unsigned long __initdata new_log_buf_len;
 /* save requested log_buf_len since it's too early to process it */
 static int __init log_buf_len_setup(char *str)
 {
-	unsigned size = memparse(str, &str);
+	unsigned int size;
+
+	if (!str)
+		return -EINVAL;
+
+	size = memparse(str, &str);
 
 	if (size)
 		size = roundup_pow_of_two(size);