diff --git a/ppl/src/main/antlr/OpenSearchPPLParser.g4 b/ppl/src/main/antlr/OpenSearchPPLParser.g4
index 0d3a328a9f..1b7739d81c 100644
--- a/ppl/src/main/antlr/OpenSearchPPLParser.g4
+++ b/ppl/src/main/antlr/OpenSearchPPLParser.g4
@@ -888,6 +888,7 @@ keywordsCanBeId
    | KMEANS
    | AD
    | ML
+   | TRENDLINE
    // commands assist keywords
    | SOURCE
    | INDEX