diff --git a/fs/cifs/cifs_debug.c b/fs/cifs/cifs_debug.c
index e6025e93c5eb01795d59cdf50ada7fd43c9b60ad..ef93d60ca4166a223d090bf6b0ec19e673cf3a70 100644
--- a/fs/cifs/cifs_debug.c
+++ b/fs/cifs/cifs_debug.c
@@ -584,6 +584,8 @@ static ssize_t cifsFYI_proc_write(struct file *file, const char __user *buffer,
 		cifsFYI = bv;
 	else if ((c[0] > '1') && (c[0] <= '9'))
 		cifsFYI = (int) (c[0] - '0'); /* see cifs_debug.h for meanings */
+	else
+		return -EINVAL;
 
 	return count;
 }