diff -urp john-1.7.4/src/rules.c john-1.7.4-mod/src/rules.c
--- john-1.7.4/src/rules.c	2009-12-24 05:02:52 +0000
+++ john-1.7.4-mod/src/rules.c	2010-01-03 18:26:56 +0000
@@ -258,7 +258,7 @@ void rules_init(int max_length)
 	rules_init_length(max_length);
 }
 
-char *rules_reject(char *rule, int split, struct db_main *db)
+char *rules_reject(char *rule, int split, char *last, struct db_main *db)
 {
 	static char out_rule[RULE_BUFFER_SIZE];
 
@@ -309,7 +309,7 @@ char *rules_reject(char *rule, int split
 accept:
 	rules_pass--;
 	strnzcpy(out_rule, rule - 1, sizeof(out_rule));
-	rules_apply("", out_rule, split, NULL);
+	rules_apply("", out_rule, split, last);
 	rules_pass++;
 
 	return out_rule;
@@ -905,15 +905,13 @@ out_OK:
 		if (length >= ARCH_SIZE - 1) {
 			if (*(ARCH_WORD *)in != *(ARCH_WORD *)last)
 				return in;
-			if (!strcmp(&in[ARCH_SIZE - 1], &last[ARCH_SIZE - 1]))
-				goto out_NULL;
-			return in;
+			if (strcmp(&in[ARCH_SIZE - 1], &last[ARCH_SIZE - 1]))
+				return in;
+			return NULL;
 		}
-		if (last[2])
-			return in;
-		if (in[0] != last[0])
+		if (last[length])
 			return in;
-		if (in[1] != last[1] && length)
+		if (memcmp(in, last, length))
 			return in;
 		return NULL;
 	}
@@ -967,7 +965,7 @@ int rules_check(struct rpp_context *star
 
 	rules_pass = -1; /* rules_reject() will turn this into -2 */
 	while ((rule = rpp_next(&ctx))) {
-		rules_reject(rule, split, NULL);
+		rules_reject(rule, split, NULL, NULL);
 		if (rules_errno) break;
 
 		if (ctx.input) rules_line = ctx.input->number;
diff -urp john-1.7.4/src/rules.h john-1.7.4-mod/src/rules.h
--- john-1.7.4/src/rules.h	2009-12-24 02:38:12 +0000
+++ john-1.7.4-mod/src/rules.h	2009-12-28 19:28:21 +0000
@@ -54,8 +54,11 @@ extern void rules_init(int max_length);
  *
  * split == 0	"single crack" mode rules allowed
  * split < 0	"single crack" mode rules are invalid
+ *
+ * last may specify which internal buffer must not be touched.
  */
-extern char *rules_reject(char *rule, int split, struct db_main *db);
+extern char *rules_reject(char *rule, int split, char *last,
+	struct db_main *db);
 
 /*
  * Applies rule to a word. Returns the updated word, or NULL if rejected or
diff -urp john-1.7.4/src/single.c john-1.7.4-mod/src/single.c
--- john-1.7.4/src/single.c	2009-12-24 00:41:54 +0000
+++ john-1.7.4-mod/src/single.c	2009-12-28 19:27:22 +0000
@@ -309,7 +309,7 @@ static void single_run(void)
 
 	saved_min = rec_rule;
 	while ((prerule = rpp_next(rule_ctx))) {
-		if (!(rule = rules_reject(prerule, 0, single_db))) {
+		if (!(rule = rules_reject(prerule, 0, NULL, single_db))) {
 			log_event("- Rule #%d: '%.100s' rejected",
 				++rule_number, prerule);
 			continue;
diff -urp john-1.7.4/src/wordlist.c john-1.7.4-mod/src/wordlist.c
--- john-1.7.4/src/wordlist.c	2009-12-24 00:42:27 +0000
+++ john-1.7.4-mod/src/wordlist.c	2009-12-28 19:28:07 +0000
@@ -194,7 +194,7 @@ void do_wordlist_crack(struct db_main *d
 	if (prerule)
 	do {
 		if (rules) {
-			if ((rule = rules_reject(prerule, -1, db))) {
+			if ((rule = rules_reject(prerule, -1, last, db))) {
 				if (strcmp(prerule, rule))
 					log_event("- Rule #%d: '%.100s'"
 						" accepted as '%.100s'",