diff --git a/examples/tests.modal b/examples/tests.modal
index 7351dbe..9f6bd51 100644
--- a/examples/tests.modal
+++ b/examples/tests.modal
@@ -88,12 +88,15 @@ reverse (modal) = ladom (reverse 1) test
 
 ?(?-) (Incomplete definitions)
 
+<> <>
+<> () ()
 <> (incomplete-basic)
 <> (incomplete-reg ?x)
 <> (waste-rule) *
 
 (incomplete-basic) = () (incomplete 1) test
 (incomplete-reg abcdef) = () (incomplete 2) test
+(?(?x) incomplete-lambda) = () (incomplete 3) test
 
 ?(?-) (Inline rules)
 
diff --git a/src/modal.c b/src/modal.c
index 221ade7..837f271 100644
--- a/src/modal.c
+++ b/src/modal.c
@@ -228,11 +228,14 @@ rewrite(void)
 			Rule *r = NULL;
 			/* phase: define */
 			if(c == '<' && s[1] == '>') {
-				r = rules_++;
+				r = rules_;
 				s = compile_rule(r, rules_ - rules - 1, s + 2);
-				if(!quiet && r->a)
-					printf("<> "), echo_rule(r, r->a), echo_rule(r, r->b), putc('\n', stdout);
-				while(*s == ' ') s++;
+				if(*r->a) {
+					if(!quiet && r->a)
+						printf("<> "), echo_rule(r, r->a), echo_rule(r, r->b), putc('\n', stdout);
+					while(*s == ' ') s++;
+					rules_++;
+				}
 				return write_tail(s);
 			}
 			/* phase: undefine */