diff --git a/diff.c b/diff.c
index 0391e8c..df62d2b 100644
--- a/diff.c
+++ b/diff.c
@@ -843,11 +843,19 @@ static int parse_num(const char **cp_p)
 
 	cnt = num = 0;
 	scale = 1;
-	while ('0' <= (ch = *cp) && ch <= '9') {
-		if (cnt++ < 5) {
-			/* We simply ignore more than 5 digits precision. */
-			scale *= 10;
-			num = num * 10 + ch - '0';
+	for(;;) {
+		ch = *cp;
+		if ( ch == '.' ) {
+			scale = 1;
+		} else if ( ch == '%' ) {
+			scale = 100;
+		} else if ( ch >= '0' && ch <= '9' ) {
+			if ( scale < 100000 ) {
+				scale *= 10;
+				num = (num*10) + (ch-'0');
+			}
+		} else {
+			break;
 		}
 		cp++;
 	}
@@ -856,7 +864,7 @@ static int parse_num(const char **cp_p)
 	/* user says num divided by scale and we say internally that
 	 * is MAX_SCORE * num / scale.
 	 */
-	return (MAX_SCORE * num / scale);
+	return (num >= scale) ? MAX_SCORE : (MAX_SCORE * num / scale);
 }
 
 int diff_scoreopt_parse(const char *opt)