diff --git a/ppl/src/main/antlr/OpenSearchPPLParser.g4 b/ppl/src/main/antlr/OpenSearchPPLParser.g4
index 1b7739d81c..c9d0f2e110 100644
--- a/ppl/src/main/antlr/OpenSearchPPLParser.g4
+++ b/ppl/src/main/antlr/OpenSearchPPLParser.g4
@@ -144,6 +144,7 @@ fillNullWithFieldVariousValues
 
 nullReplacementExpression
    : nullableField = fieldExpression EQUAL nullReplacement = valueExpression
+   ;
 
 trendlineCommand
    : TRENDLINE (SORT sortField)? trendlineClause (trendlineClause)*