diff --git a/Database/Bloodhound/Types.hs b/Database/Bloodhound/Types.hs
index b6fd495..bad55da 100644
--- a/Database/Bloodhound/Types.hs
+++ b/Database/Bloodhound/Types.hs
@@ -60,6 +60,7 @@ module Database.Bloodhound.Types
        , GreaterThanEq(..)
        , Regexp(..)
        , RegexpFlags(..)
+       , RegexpFlag(..)
        , FieldName(..)
        , IndexName(..)
        , MappingName(..)
@@ -144,6 +145,7 @@ module Database.Bloodhound.Types
 
 import Data.Aeson
 import qualified Data.ByteString.Lazy.Char8 as L
+import Data.List.NonEmpty (NonEmpty)
 import Data.Text (Text)
 import qualified Data.Text as T
 import Data.Time.Clock (UTCTime)
@@ -824,7 +826,17 @@ data RangeExecution = RangeExecutionIndex
                     | RangeExecutionFielddata deriving (Eq, Show)
 
 newtype Regexp = Regexp Text deriving (Eq, Show)
-newtype RegexpFlags = RegexpFlags Text deriving (Eq, Show)
+
+data RegexpFlags = AllRegexpFlags
+                 | NoRegexpFlags
+                 | SomeRegexpFlags (NonEmpty RegexpFlag) deriving (Eq, Show)
+
+data RegexpFlag = AnyString
+                | Automaton
+                | Complement
+                | Empty
+                | Intersection
+                | Interval deriving (Eq, Show)
 
 halfRangeToKV :: HalfRange -> (Text, Double)
 halfRangeToKV (HalfRangeLt  (LessThan n))      = ("lt",  n)
diff --git a/Database/Bloodhound/Types/Instances.hs b/Database/Bloodhound/Types/Instances.hs
index a2ed035..f8c66f0 100644
--- a/Database/Bloodhound/Types/Instances.hs
+++ b/Database/Bloodhound/Types/Instances.hs
@@ -8,6 +8,8 @@ module Database.Bloodhound.Types.Instances
 
 import Control.Applicative
 import Data.Aeson
+import Data.List (nub)
+import Data.List.NonEmpty (NonEmpty(..))
 import Data.Maybe (catMaybes)
 import Data.Monoid
 import qualified Data.Text as T
@@ -57,7 +59,7 @@ instance ToJSON Filter where
                    , "distance_type" .= toJSON distanceType
                    , "optimize_bbox" .= optimizeBbox
                    , distanceGeoField .= toJSON geoDistLatLon
-                   , "_cache" .= cache]]                   
+                   , "_cache" .= cache]]
 
   toJSON (GeoDistanceRangeFilter (GeoPoint (FieldName gddrField) drLatLon)
           (DistanceRange geoDistRangeDistFrom drDistanceTo)) =
@@ -213,7 +215,7 @@ instance ToJSON Query where
   toJSON (QueryRangeQuery query) =
     object [ "range"  .= toJSON query ]
 
-  toJSON (QueryRegexpQuery query) = 
+  toJSON (QueryRegexpQuery query) =
     object [ "regexp" .= toJSON query ]
 
   toJSON (QuerySimpleQueryStringQuery query) =
@@ -645,7 +647,7 @@ instance ToJSON SortSpec where
 
 
 instance ToJSON SortOrder where
-  toJSON Ascending  = String "asc"      
+  toJSON Ascending  = String "asc"
   toJSON Descending = String "desc"
 
 
@@ -731,8 +733,16 @@ instance ToJSON RangeExecution where
 
 
 instance ToJSON RegexpFlags where
-  toJSON (RegexpFlags txt) = String txt
-
+  toJSON AllRegexpFlags              = String "ALL"
+  toJSON NoRegexpFlags               = String "NONE"
+  toJSON (SomeRegexpFlags (h :| fs)) = String $ T.intercalate "|" flagStrs
+    where flagStrs             = map flagStr . nub $ h:fs
+          flagStr AnyString    = "ANYSTRING"
+          flagStr Automaton    = "AUTOMATON"
+          flagStr Complement   = "COMPLEMENT"
+          flagStr Empty        = "EMPTY"
+          flagStr Intersection = "INTERSECTION"
+          flagStr Interval     = "INTERVAL"
 
 instance ToJSON Term where
   toJSON (Term field value) = object ["term" .= object
diff --git a/bloodhound.cabal b/bloodhound.cabal
index 54c1ebc..13b07e2 100644
--- a/bloodhound.cabal
+++ b/bloodhound.cabal
@@ -29,6 +29,7 @@ library
                        aeson            >= 0.7,
                        conduit          >= 1.0,
                        http-client      >= 0.3,
+                       semigroups       >= 0.15,
                        time             >= 1.4,
                        text             >= 0.11,
                        http-types       >= 0.8
@@ -47,5 +48,7 @@ test-suite tests
                        hspec                >= 1.8,
                        text                 >= 0.11,
                        time                 >= 1.4,
-                       aeson                >= 0.7
+                       aeson                >= 0.7,
+                       semigroups           >= 0.15,
+                       QuickCheck
   default-language:    Haskell2010
diff --git a/tests/tests.hs b/tests/tests.hs
index bb97f44..dc26cf4 100644
--- a/tests/tests.hs
+++ b/tests/tests.hs
@@ -1,17 +1,24 @@
 {-# LANGUAGE DeriveGeneric #-}
+{-# LANGUAGE ScopedTypeVariables #-}
 
 module Main where
 
+import Control.Applicative
 import Database.Bloodhound
 import Data.Aeson
+import Data.List (nub)
+import Data.List.NonEmpty (NonEmpty(..))
 import Data.Time.Calendar (Day(..))
 import Data.Time.Clock (secondsToDiffTime, UTCTime(..))
 import Data.Text (Text)
+import qualified Data.Text as T
 import GHC.Generics (Generic)
 import Network.HTTP.Client
 import qualified Network.HTTP.Types.Status as NHTS
 import Prelude hiding (filter, putStrLn)
 import Test.Hspec
+import Test.Hspec.QuickCheck (prop)
+import Test.QuickCheck
 
 testServer  :: Server
 testServer  = Server "http://localhost:9200"
@@ -104,6 +111,27 @@ data BulkTest = BulkTest { name :: Text } deriving (Eq, Generic, Show)
 instance FromJSON BulkTest
 instance ToJSON BulkTest
 
+noDuplicates :: Eq a => [a] -> Bool
+noDuplicates xs = nub xs == xs
+
+instance Arbitrary RegexpFlags where
+  arbitrary = oneof [ pure AllRegexpFlags
+                    , pure NoRegexpFlags
+                    , SomeRegexpFlags <$> arbitrary
+                    ]
+
+instance Arbitrary a => Arbitrary (NonEmpty a) where
+  arbitrary = liftA2 (:|) arbitrary arbitrary
+
+instance Arbitrary RegexpFlag where
+  arbitrary = oneof [ pure AnyString
+                    , pure Automaton
+                    , pure Complement
+                    , pure Empty
+                    , pure Intersection
+                    , pure Interval
+                    ]
+
 main :: IO ()
 main = hspec $ do
 
@@ -314,7 +342,7 @@ main = hspec $ do
     it "returns document for regexp filter" $ do
       _ <- insertData
       let filter = RegexpFilter (FieldName "user") (Regexp "bite.*app")
-                   (RegexpFlags "ALL") (CacheName "test") False (CacheKey "key")
+                   AllRegexpFlags (CacheName "test") False (CacheKey "key")
       let search = mkSearch Nothing (Just filter)
       myTweet <- searchTweet search
       myTweet `shouldBe` Right exampleTweet
@@ -322,7 +350,26 @@ main = hspec $ do
     it "doesn't return document for non-matching regexp filter" $ do
       _ <- insertData
       let filter = RegexpFilter (FieldName "user")
-                   (Regexp "boy") (RegexpFlags "ALL")
+                   (Regexp "boy") AllRegexpFlags
                    (CacheName "test") False (CacheKey "key")
       let search = mkSearch Nothing (Just filter)
       searchExpectNoResults search
+  describe "ToJSON RegexpFlags" $ do
+    it "generates the correct JSON for AllRegexpFlags" $
+      toJSON AllRegexpFlags `shouldBe` String "ALL"
+
+    it "generates the correct JSON for NoRegexpFlags" $
+      toJSON NoRegexpFlags `shouldBe` String "NONE"
+
+    it "generates the correct JSON for SomeRegexpFlags" $
+      let flags = AnyString :| [ Automaton
+                               , Complement
+                               , Empty
+                               , Intersection
+                               , Interval ]
+      in toJSON (SomeRegexpFlags flags) `shouldBe` String "ANYSTRING|AUTOMATON|COMPLEMENT|EMPTY|INTERSECTION|INTERVAL"
+
+    prop "removes duplicates from flags" $ \(flags :: RegexpFlags) ->
+      let String str = toJSON flags
+          flagStrs   = T.splitOn "|" str
+      in noDuplicates flagStrs