1 files changed, 1 insertions, 1 deletions

diff --git a/subprojects/frontend/src/language/problem.grammar b/subprojects/frontend/src/language/problem.grammar
index 1e1ef70f..d630b9c4 100644
--- a/subprojects/frontend/src/language/problem.grammar
+++ b/subprojects/frontend/src/language/problem.grammar
@@ -153,7 +153,7 @@ sep1<separator, content> { content (separator content)* }
     "\"" (![\\"\n] | "\\" (![\n] | "\n"))* "\""
   }
 
-  ComparisonOp { ">" | ">=" | "<" | "<=" | "==" }
+  ComparisonOp { ">" | ">=" | "<" | "<=" | "==" | "!=" }
 
   NotOp { "!" }