diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index aedc7f4d6048..8530d651e8fb 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -1022,7 +1022,12 @@ static void __init log_buf_len_update(unsigned size)
 /* 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);
 
 	log_buf_len_update(size);