diff --git a/makefile b/makefile
index cf49fed..24e2457 100644
--- a/makefile
+++ b/makefile
@@ -13,6 +13,8 @@ debug: all bin/modal-debug
 	@ bin/modal-debug examples/hello.modal
 test: all bin/modal-debug bin/modal
 	@ bin/modal -v
+	@ bin/modal-debug -q examples/fizzbuzz.modal
+	@ bin/modal-debug -q examples/sierpinski.modal
 	@ bin/modal-debug -q examples/tests.modal
 install: bin/modal
 	cp bin/modal ~/bin/
diff --git a/src/modal.c b/src/modal.c
index 8296df0..de10d82 100644
--- a/src/modal.c
+++ b/src/modal.c
@@ -129,9 +129,9 @@ apply_rule(Rule *r, char *s)
 	if(!(c = *s) || spacer(c)) {
 		char *b = r->b, *origin = dst_;
 		while((c = *b++)) {
-			if(c == '?' && (unsigned int)(*b - '0') < 9) {
+			if(c == '?') {
 				unsigned int id = *b - '0';
-				if((reg = regs[id])) {
+				if(id < 9 && (reg = regs[id])) {
 					b++;
 					if(!write_reg(r->key[id], reg) && dst_ != origin) dst_--;
 				} else