diff --git a/common/parse_base10.s b/common/parse_base10.s
index 7478906..7a9f446 100644
--- a/common/parse_base10.s
+++ b/common/parse_base10.s
@@ -3,7 +3,9 @@
 	.global _parse_base10
 _parse_base10:
 	/* r8 = pointer to text ; r1 = number */
+	/* return r0 = number of digits */
 	mov	#0,r1	/* r1: accumulated number */
+	mov	r8,r0	/* r0: number of digits */
 parse_base10_loop:
 	mov.b 	@r8+,r2
 	add	#-48,r2 /* ascii '0' */
@@ -19,4 +21,4 @@ parse_base10_loop:
 	add	r2,r1
 parse_base10_rts:
 	rts
-	nop
+	sub	r8,r0