diff --git a/src/backend/tsearch/to_tsany.c b/src/backend/tsearch/to_tsany.c
index f4ddfc0105..15d754564e 100644
--- a/src/backend/tsearch/to_tsany.c
+++ b/src/backend/tsearch/to_tsany.c
@@ -252,6 +252,8 @@ to_tsvector_byid(PG_FUNCTION_ARGS)
 												 * number */
 	if (prs.lenwords < 2)
 		prs.lenwords = 2;
+	else if (prs.lenwords > MaxAllocSize / sizeof(ParsedWord))
+		prs.lenwords = MaxAllocSize / sizeof(ParsedWord);
 	prs.curwords = 0;
 	prs.pos = 0;
 	prs.words = (ParsedWord *) palloc(sizeof(ParsedWord) * prs.lenwords);