diff --git a/src/PostgREST/ApiRequest.hs b/src/PostgREST/ApiRequest.hs
index f154f05cd51..f82606f2dd2 100644
--- a/src/PostgREST/ApiRequest.hs
+++ b/src/PostgREST/ApiRequest.hs
@@ -70,6 +70,32 @@ data Target = TargetIdent QualifiedIdentifier
             | TargetUnknown [Text]
             deriving Eq
 
+-- | RPC query param value `/rpc/func?v=<value>`, used for VARIADIC functions on form-urlencoded POST and GETs
+-- | It can be fixed `?v=1` or repeated `?v=1&v=2&v=3.
+data RpcParamValue = Fixed Text | Variadic [Text]
+instance JSON.ToJSON RpcParamValue where
+  toJSON (Fixed    v) = JSON.toJSON v
+  toJSON (Variadic v) = JSON.toJSON v
+
+toRpcParamValue :: ProcDescription -> (Text, Text) -> (Text, RpcParamValue)
+toRpcParamValue proc (k, v) | argIsVariadic k = (k, Variadic [v])
+                            | otherwise       = (k, Fixed v)
+  where
+    argIsVariadic arg = isJust $ find (\PgArg{pgaName, pgaVar} -> pgaName == arg && pgaVar) $ pdArgs proc
+
+-- | Convert rpc params `/rpc/func?a=val1&b=val2` to json `{"a": "val1", "b": "val2"}
+jsonRpcParams :: ProcDescription -> [(Text, Text)] -> PayloadJSON
+jsonRpcParams proc prms =
+  if not $ pdHasVariadic proc then -- if proc has no variadic arg, save steps and directly convert to json
+    ProcessedJSON (JSON.encode $ M.fromList $ second JSON.toJSON <$> prms) (S.fromList $ fst <$> prms)
+  else
+    let paramsMap = M.fromListWith mergeParams $ toRpcParamValue proc <$> prms in
+    ProcessedJSON (JSON.encode paramsMap) (S.fromList $ M.keys paramsMap)
+  where
+    mergeParams :: RpcParamValue -> RpcParamValue -> RpcParamValue
+    mergeParams (Variadic a) (Variadic b) = Variadic $ b ++ a
+    mergeParams _ v                       = v -- repeated params for non-variadic arguments are not merged
+
 {-|
   Describes what the user wants to do. This data type is a
   translation of the raw elements of an HTTP request into domain
@@ -187,33 +213,27 @@ userApiRequest confSchemas rootSpec dbStructure req reqBody
         (Just ProcessedJSON{pjKeys}, _) -> pjKeys
         (Just RawJSON{}, Just cls)      -> cls
         _                               -> S.empty
-  payload =
-    case (contentType, action) of
-      (_, ActionInvoke InvGet)  -> Right rpcPrmsToJson
-      (_, ActionInvoke InvHead) -> Right rpcPrmsToJson
-      (CTApplicationJSON, _) ->
-        if isJust columns
-          then Right $ RawJSON reqBody
-          else note "All object keys must match" . payloadAttributes reqBody
-                 =<< if BL.null reqBody && isTargetingProc
-                       then Right emptyObject
-                       else JSON.eitherDecode reqBody
-      (CTTextCSV, _) -> do
-        json <- csvToJson <$> CSV.decodeByName reqBody
-        note "All lines must have same number of fields" $ payloadAttributes (JSON.encode json) json
-      (CTUrlEncoded, _) ->
-        let json = paramsFromList . map (toS *** toS) . parseSimpleQuery $ toS reqBody
-            keys = S.fromList $ M.keys json in
-        Right $ ProcessedJSON (JSON.encode json) keys
-      (ct, _) ->
-        Left $ toS $ "Content-Type not acceptable: " <> toMime ct
-  rpcPrmsToJson = ProcessedJSON (JSON.encode $ paramsFromList rpcQParams) (S.fromList $ fst <$> rpcQParams)
-  paramsFromList ls = M.fromListWith mergeParams $ toRpcParamsWith isVariadic ls
-    where
-      isVariadic k =
-        case target of
-          TargetProc{tProc} -> argIsVariadic tProc k
-          _                 -> False
+  payload = case contentType of
+    CTApplicationJSON ->
+      if isJust columns
+        then Right $ RawJSON reqBody
+        else note "All object keys must match" . payloadAttributes reqBody
+               =<< if BL.null reqBody && isTargetingProc
+                     then Right emptyObject
+                     else JSON.eitherDecode reqBody
+    CTTextCSV -> do
+      json <- csvToJson <$> CSV.decodeByName reqBody
+      note "All lines must have same number of fields" $ payloadAttributes (JSON.encode json) json
+    CTUrlEncoded ->
+      let urlEncodedBody = parseSimpleQuery $ toS reqBody in
+      case target of
+        TargetProc{tProc} ->
+          Right $ jsonRpcParams tProc $ (toS *** toS) <$> urlEncodedBody
+        _ ->
+          let paramsMap = M.fromList $ (toS *** JSON.String . toS) <$> urlEncodedBody in
+          Right $ ProcessedJSON (JSON.encode paramsMap) $ S.fromList (M.keys paramsMap)
+    ct ->
+      Left $ toS $ "Content-Type not acceptable: " <> toMime ct
   topLevelRange = fromMaybe allRange $ M.lookup "limit" ranges -- if no limit is specified, get all the request rows
   action =
     case method of
@@ -257,16 +277,14 @@ userApiRequest confSchemas rootSpec dbStructure req reqBody
       ["rpc", pName] -> TargetProc (callFindProc pName) False
       other          -> TargetUnknown other
 
-  shouldParsePayload =
-    action `elem`
-    [ActionCreate, ActionUpdate, ActionSingleUpsert,
-    ActionInvoke InvPost,
-    -- Though ActionInvoke{isGet=True}(a GET /rpc/..) doesn't really have a payload, we use the payload variable as a way
+  shouldParsePayload = action `elem` [ActionCreate, ActionUpdate, ActionSingleUpsert, ActionInvoke InvPost]
+  relevantPayload = case (target, action) of
+    -- Though ActionInvoke GET/HEAD doesn't really have a payload, we use the payload variable as a way
     -- to store the query string arguments to the function.
-    ActionInvoke InvGet,
-    ActionInvoke InvHead]
-  relevantPayload | shouldParsePayload = rightToMaybe payload
-                  | otherwise = Nothing
+    (TargetProc{tProc}, ActionInvoke InvGet)  -> Just $ jsonRpcParams tProc rpcQParams
+    (TargetProc{tProc}, ActionInvoke InvHead) -> Just $ jsonRpcParams tProc rpcQParams
+    _ | shouldParsePayload                    -> rightToMaybe payload
+      | otherwise                             -> Nothing
   path            = pathInfo req
   method          = requestMethod req
   hdrs            = requestHeaders req
diff --git a/src/PostgREST/DbStructure.hs b/src/PostgREST/DbStructure.hs
index e3d563d1809..3cb456159e2 100644
--- a/src/PostgREST/DbStructure.hs
+++ b/src/PostgREST/DbStructure.hs
@@ -128,7 +128,7 @@ sourceColumnFromRow allCols (s1,t1,c1,s2,t2,c2) = (,) <$> col1 <*> col2
 decodeProcs :: HD.Result ProcsMap
 decodeProcs =
   -- Duplicate rows for a function means they're overloaded, order these by least args according to ProcDescription Ord instance
-  map sort . M.fromListWith (++) . map ((\(x,y) -> (x, [y])) . addKey) <$> HD.rowList procRow
+  map sort . M.fromListWith (++) . map ((\(x,y) -> (x, [y])) . addKey . addHasVariadic) <$> HD.rowList procRow
   where
     procRow = ProcDescription
               <$> column HD.text
@@ -141,6 +141,10 @@ decodeProcs =
                   <*> column HD.bool
                   <*> column HD.char)
               <*> (parseVolatility <$> column HD.char)
+              <*> pure False
+
+    addHasVariadic :: ProcDescription -> ProcDescription
+    addHasVariadic pd@ProcDescription{pdArgs} = pd{pdHasVariadic=isJust $ find pgaVar pdArgs}
 
     addKey :: ProcDescription -> (QualifiedIdentifier, ProcDescription)
     addKey pd = (QualifiedIdentifier (pdSchema pd) (pdName pd), pd)
diff --git a/src/PostgREST/Types.hs b/src/PostgREST/Types.hs
index 377a8f4316c..56964e71b5e 100644
--- a/src/PostgREST/Types.hs
+++ b/src/PostgREST/Types.hs
@@ -4,7 +4,6 @@ Description : PostgREST common types and functions used by the rest of the modul
 -}
 {-# LANGUAGE DeriveGeneric         #-}
 {-# LANGUAGE DuplicateRecordFields #-}
-{-# LANGUAGE NamedFieldPuns        #-}
 
 module PostgREST.Types where
 
@@ -148,14 +147,15 @@ data ProcDescription = ProcDescription {
 , pdArgs        :: [PgArg]
 , pdReturnType  :: RetType
 , pdVolatility  :: ProcVolatility
+, pdHasVariadic :: Bool
 } deriving (Show, Eq)
 
 -- Order by least number of args in the case of overloaded functions
 instance Ord ProcDescription where
-  ProcDescription schema1 name1 des1 args1 rt1 vol1 `compare` ProcDescription schema2 name2 des2 args2 rt2 vol2
+  ProcDescription schema1 name1 des1 args1 rt1 vol1 hasVar1 `compare` ProcDescription schema2 name2 des2 args2 rt2 vol2 hasVar2
     | schema1 == schema2 && name1 == name2 && length args1 < length args2  = LT
     | schema2 == schema2 && name1 == name2 && length args1 > length args2  = GT
-    | otherwise = (schema1, name1, des1, args1, rt1, vol1) `compare` (schema2, name2, des2, args2, rt2, vol2)
+    | otherwise = (schema1, name1, des1, args1, rt1, vol1, hasVar1) `compare` (schema2, name2, des2, args2, rt2, vol2, hasVar2)
 
 -- | A map of all procs, all of which can be overloaded(one entry will have more than one ProcDescription).
 -- | It uses a HashMap for a faster lookup.
@@ -171,7 +171,7 @@ findProc qi payloadKeys paramsAsSingleObject allProcs = fromMaybe fallback bestM
   where
     -- instead of passing Maybe ProcDescription around, we create a fallback description here when we can't find a matching function
     -- args is empty, but because "specifiedProcArgs" will fill the missing arguments with default type text, this is not a problem
-    fallback = ProcDescription (qiSchema qi) (qiName qi) Nothing mempty (SetOf $ Composite $ QualifiedIdentifier "" "record") Volatile
+    fallback = ProcDescription (qiSchema qi) (qiName qi) Nothing mempty (SetOf $ Composite $ QualifiedIdentifier mempty "record") Volatile False
     bestMatch =
       case M.lookup qi allProcs of
         Nothing     -> Nothing
@@ -202,12 +202,6 @@ procTableName proc = case pdReturnType proc of
   Single (Composite qi) -> Just $ qiName qi
   _                     -> Nothing
 
-argIsVariadic :: ProcDescription -> Text -> Bool
-argIsVariadic proc arg =
-  case find (\PgArg{pgaName} -> pgaName == arg) $ pdArgs proc of
-    Just PgArg{pgaVar} -> pgaVar
-    _                  -> False
-
 type Schema = Text
 type TableName = Text
 
@@ -414,26 +408,6 @@ type Alias = Text
 type Cast = Text
 type NodeName = Text
 
--- RPC query param, used for POST of form-data and GET requests
-data RpcParamValue = Fixed Text | Variadic [Text]
-
-mergeParams :: RpcParamValue -> RpcParamValue -> RpcParamValue
-mergeParams (Variadic a) (Variadic b) = Variadic $ b ++ a
--- repeated params for non-variadic arguments are not merged
-mergeParams _ v                       = v
-
-instance JSON.ToJSON RpcParamValue where
-  toJSON (Fixed    v) = JSON.toJSON v
-  toJSON (Variadic v) = JSON.toJSON v
-
-type RpcParams = [(Text, RpcParamValue)]
-
-toRpcParamsWith :: (Text -> Bool) -> [(Text, Text)] -> RpcParams
-toRpcParamsWith isVariadic ls = toRpcParamValue <$> ls
-  where
-    toRpcParamValue (k, v)
-      | isVariadic k = (k, Variadic [v])
-      | otherwise    = (k, Fixed v)
 
 {-|
   Custom guc header, it's obtained by parsing the json in a:
diff --git a/test/Feature/JsonOperatorSpec.hs b/test/Feature/JsonOperatorSpec.hs
index 9f0d47f3e7d..094f5b8f8dc 100644
--- a/test/Feature/JsonOperatorSpec.hs
+++ b/test/Feature/JsonOperatorSpec.hs
@@ -7,7 +7,8 @@ import Test.Hspec
 import Test.Hspec.Wai
 import Test.Hspec.Wai.JSON
 
-import PostgREST.Types (PgVersion, pgVersion112, pgVersion121, pgVersion95)
+import PostgREST.Types (PgVersion, pgVersion112, pgVersion121,
+                        pgVersion95)
 import Protolude       hiding (get)
 import SpecHelper
 
diff --git a/test/Feature/QuerySpec.hs b/test/Feature/QuerySpec.hs
index b27c21385f2..823c824716f 100644
--- a/test/Feature/QuerySpec.hs
+++ b/test/Feature/QuerySpec.hs
@@ -10,7 +10,8 @@ import Test.Hspec.Wai.JSON
 
 import Text.Heredoc
 
-import PostgREST.Types (PgVersion, pgVersion96, pgVersion112, pgVersion121)
+import PostgREST.Types (PgVersion, pgVersion112, pgVersion121,
+                        pgVersion96)
 import Protolude       hiding (get)
 import SpecHelper
 
diff --git a/test/Feature/RpcPreRequestGucsSpec.hs b/test/Feature/RpcPreRequestGucsSpec.hs
index 77ff5120b0a..9afc7a9a683 100644
--- a/test/Feature/RpcPreRequestGucsSpec.hs
+++ b/test/Feature/RpcPreRequestGucsSpec.hs
@@ -11,7 +11,7 @@ import Test.Hspec.Wai
 import Test.Hspec.Wai.JSON
 import Text.Heredoc
 
-import Protolude       hiding (get)
+import Protolude  hiding (get)
 import SpecHelper
 
 spec :: SpecWith ((), Application)
diff --git a/test/Feature/RpcSpec.hs b/test/Feature/RpcSpec.hs
index ca2716e6a7f..b894fab1ccd 100644
--- a/test/Feature/RpcSpec.hs
+++ b/test/Feature/RpcSpec.hs
@@ -3,7 +3,7 @@ module Feature.RpcSpec where
 import qualified Data.ByteString.Lazy as BL (empty)
 
 import Network.Wai      (Application)
-import Network.Wai.Test (SResponse (simpleBody, simpleStatus, simpleHeaders))
+import Network.Wai.Test (SResponse (simpleBody, simpleHeaders, simpleStatus))
 
 import Network.HTTP.Types
 import Test.Hspec          hiding (pendingWith)
@@ -523,8 +523,8 @@ spec actualPgVersion =
               `shouldRespondWith`
                 [json|["hi", "there"]|]
 
-    it "returns first value for repeated params without VARIADIC" $
-      get "/rpc/sayhello?name=world&name=ignored"
+    it "returns last value for repeated params without VARIADIC" $
+      get "/rpc/sayhello?name=ignored&name=world"
         `shouldRespondWith`
           [json|"Hello, world"|]