1 files changed, 1 insertions, 1 deletions

diff --git a/subprojects/language/src/main/java/tools/refinery/language/Problem.xtext b/subprojects/language/src/main/java/tools/refinery/language/Problem.xtext
index f514e96c..2a8429a3 100644
--- a/subprojects/language/src/main/java/tools/refinery/language/Problem.xtext
+++ b/subprojects/language/src/main/java/tools/refinery/language/Problem.xtext
@@ -72,7 +72,7 @@ NegativeLiteral:
         modality=Modality? "!" atom=Atom;
 
 enum ComparisonOp:
-        LESS="<" | LESS_EQ="<=" | GREATER=">" | GREATER_EQ=">=" | EQ="==";
+        LESS="<" | LESS_EQ="<=" | GREATER=">" | GREATER_EQ=">=" | EQ="==" | NOT_EQ="!=";
 
 CountLiteral:
         modality=Modality? "count" atom=Atom op=ComparisonOp threshold=INT;