1 files changed, 1 insertions, 1 deletions

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)+ }