diff --git a/arch/mn10300/mm/misalignment.c b/arch/mn10300/mm/misalignment.c
index 614c32b6..066ddc6 100644
--- a/arch/mn10300/mm/misalignment.c
+++ b/arch/mn10300/mm/misalignment.c
@@ -543,7 +543,7 @@
 {
 	unsigned long *postinc = NULL, address = 0, tmp;
 
-	params &= 0x7fffffff;
+	params &= 0x00ffffff;
 
 	do {
 		switch (params & 0xff) {
@@ -631,6 +631,7 @@
 			address += disp;
 			break;
 		default:
+			BUG();
 			return 0;
 		}
 	} while ((params >>= 8));
@@ -697,6 +698,7 @@
 		break;
 
 	default:
+		BUG();
 		return 0;
 	}