diff --git a/src/modal.c b/src/modal.c
index fd54d02..e159e28 100644
--- a/src/modal.c
+++ b/src/modal.c
@@ -5,7 +5,7 @@ typedef struct {
 	char *a, *b;
 } Rule;
 
-static int flip, cycles = 0x10000;
+static int flip, rmin = 0xff, rmax = 0x00, cycles = 0x10000;
 static Rule rules[0x1000], lambda, *rules_ = rules;
 static char dict[0x8000], *dict_ = dict;
 static char bank_a[0x4000], *src_ = bank_a;
@@ -37,8 +37,11 @@ set_reg(int r, char *b)
 		char *a = regs[r], *aa = walk(a), *bb = walk(b);
 		while(a < aa && b < bb)
 			if(*a++ != *b++) return 0;
-	} else
+	} else {
 		regs[r] = b;
+		if(r < rmin) rmin = r;
+		if(r > rmax) rmax = r;
+	}
 	return 1;
 }
 
@@ -87,8 +90,11 @@ match_rule(Rule *r, char *p)
 {
 	int i;
 	char c, last = 0, *a = r->a, *b = p;
-	for(i = 0x21; i < 0x7f; i++)
-		regs[i] = 0;
+	if(rmax) {
+		for(i = 0; i <= rmax; i++)
+			regs[i] = 0;
+		rmin = 0xff, rmax = 0x00;
+	}
 	while((c = *a)) {
 		if(spacer(last) && c == '?') {
 			if(!set_reg(*(++a), b)) return NULL;