diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9b395c5b9..107e513f8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -29,7 +29,7 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 
  - #2444, Removed `db-pool-timeout` option, because this was removed upstream in hasql-pool. - @robx
  - #2343, PATCH requests that don't affect any rows no longer return 404 - @wolfgangwalther
- - #2537, Stricter parsing of query string. Instead of silently ignoring, the parser now throws on invalid syntax like json paths for embeddings, hints for regular columns, empty casts, etc. - @wolfgangwalther
+ - #2537, Stricter parsing of query string. Instead of silently ignoring, the parser now throws on invalid syntax like json paths for embeddings, hints for regular columns, empty casts or fts languages, etc. - @wolfgangwalther
 
 ### Deprecated
 
diff --git a/src/PostgREST/ApiRequest/QueryParams.hs b/src/PostgREST/ApiRequest/QueryParams.hs
index 82bb00eb0..acd1bb51f 100644
--- a/src/PostgREST/ApiRequest/QueryParams.hs
+++ b/src/PostgREST/ApiRequest/QueryParams.hs
@@ -518,6 +518,12 @@ pFieldSelect = lexeme $
            try (void $ lookAhead (string ",")) <|>
            try eof
 
+-- |
+-- Parse operator expression used in horizontal filtering
+--
+-- >>> P.parse (pOpExpr pSingleVal) "" "fts().value"
+-- Left (line 1, column 7):
+-- unknown single value operator fts()
 pOpExpr :: Parser SingleVal -> Parser OpExpr
 pOpExpr pSVal = try ( string "not" *> pDelimiter *> (OpExpr True <$> pOperation)) <|> OpExpr False <$> pOperation
   where
@@ -541,7 +547,7 @@ pOpExpr pSVal = try ( string "not" *> pDelimiter *> (OpExpr True <$> pOperation)
     pFts = do
       opStr <- try (P.many (noneOf ".("))
       op <- parseMaybe ("unknown fts operator " <> opStr) . ftsOperator $ toS opStr
-      lang <- optionMaybe $ try (between (char '(') (char ')') $ many pIdentifierChar)
+      lang <- optionMaybe $ try (between (char '(') (char ')') $ many1 pIdentifierChar)
       pDelimiter >> Fts op (toS <$> lang) <$> pSVal
 
     parseMaybe :: [Char] -> Maybe a -> Parser a