diff --git a/lib/reed_solomon/decode_rs.c b/lib/reed_solomon/decode_rs.c
index 3313bf944ff142ecf7fd24a274ed52dd98ca4d81..22006eaa41e65c28bd89a9fbfb9ed111032487f6 100644
--- a/lib/reed_solomon/decode_rs.c
+++ b/lib/reed_solomon/decode_rs.c
@@ -39,7 +39,7 @@
 
 	/* Check length parameter for validity */
 	pad = nn - nroots - len;
-	BUG_ON(pad < 0 || pad >= nn);
+	BUG_ON(pad < 0 || pad >= nn - nroots);
 
 	/* Does the caller provide the syndrome ? */
 	if (s != NULL)