diff --git a/ppl/src/main/antlr/OpenSearchPPLParser.g4 b/ppl/src/main/antlr/OpenSearchPPLParser.g4
index 98129917ff..bbcef18d71 100644
--- a/ppl/src/main/antlr/OpenSearchPPLParser.g4
+++ b/ppl/src/main/antlr/OpenSearchPPLParser.g4
@@ -870,6 +870,7 @@ keywordsCanBeId
    | KMEANS
    | AD
    | ML
+   | TRENDLINE
    // commands assist keywords
    | SOURCE
    | INDEX