2 files changed, 2 insertions, 2 deletions

diff --git a/subprojects/frontend/src/index.tsx b/subprojects/frontend/src/index.tsx
index 78e469cd..152c0bf7 100644
--- a/subprojects/frontend/src/index.tsx
+++ b/subprojects/frontend/src/index.tsx
@@ -34,7 +34,7 @@ pred invalidTaxStatus(Person p) <->
     parent(p, q),
     !taxStatus(q, retired).
 
-rule createChild(p, newPerson):
+rule createChild(may Person p, must Person newPerson):
     may children(p, newPerson),
     may !equals(newPerson, newPerson)
 ==> new q <: newPerson,
diff --git a/subprojects/frontend/src/language/problem.grammar b/subprojects/frontend/src/language/problem.grammar
index f3794e27..ac0b0ea3 100644
--- a/subprojects/frontend/src/language/problem.grammar
+++ b/subprojects/frontend/src/language/problem.grammar
@@ -51,7 +51,7 @@ ReferenceDeclaration {
   ";"?
 }
 
-Parameter { RelationName? VariableName }
+Parameter { Modality? RelationName? VariableName }
 
 Conjunction { ("," | Literal)+ }