diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,9 @@
+0.4.0.0
+-------
+* Allow passing the base URL dynamically in Elm. (#20)
+* Don't use `toString` on `Text` parameters. (domenkozar) (#23, #24)
+* Fix query parameter generation. (domenkozar) (#25)
+
 0.3.0.1
 -------
 * Prefix generated function arguments to ensure valid Elm identifiers (#21)
diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -84,18 +84,17 @@
         |> required "name" string
 
 getBooksByBookId : Int -> Http.Request (Book)
-getBooksByBookId bookId =
+getBooksByBookId capture_bookId =
     Http.request
         { method =
             "GET"
         , headers =
-            [ Http.header "Content-Type" "application/json"
-            ]
+            []
         , url =
             String.join "/"
                 [ ""
                 , "books"
-                , bookId |> toString |> Http.encodeUri
+                , capture_bookId |> toString |> Http.encodeUri
                 ]
         , body =
             Http.emptyBody
diff --git a/examples/books/generate.hs b/examples/books/generate.hs
--- a/examples/books/generate.hs
+++ b/examples/books/generate.hs
@@ -8,7 +8,7 @@
 import           GHC.Generics (Generic)
 import           Servant.API  ((:<|>), (:>), Capture, Get, JSON, Post, ReqBody)
 import           Servant.Elm  (ElmOptions (..), ElmType, Proxy (Proxy),
-                               defElmImports, defElmOptions,
+                               UrlPrefix (Static), defElmImports, defElmOptions,
                                generateElmForAPIWith)
 
 data Book = Book
@@ -22,7 +22,7 @@
            :<|> "books" :> Capture "bookId" Int :> Get '[JSON] Book
 
 myElmOpts :: ElmOptions
-myElmOpts = defElmOptions { urlPrefix = "http://localhost:8000" }
+myElmOpts = defElmOptions { urlPrefix = Static "http://localhost:8000" }
 
 spec :: Spec
 spec = Spec ["Generated", "BooksApi"]
diff --git a/examples/e2e-tests/generate.hs b/examples/e2e-tests/generate.hs
--- a/examples/e2e-tests/generate.hs
+++ b/examples/e2e-tests/generate.hs
@@ -10,12 +10,12 @@
 import           Servant.API  ((:<|>), (:>), Capture, Get, GetNoContent, JSON,
                                NoContent, Post, QueryParam, ReqBody)
 import           Servant.Elm  (ElmOptions (..), ElmType, Proxy (Proxy),
-                               defElmImports, defElmOptions,
+                               UrlPrefix (Static), defElmImports, defElmOptions,
                                generateElmForAPIWith)
 
 
 myElmOpts :: ElmOptions
-myElmOpts = defElmOptions { urlPrefix =  "https://httpbin.org" }
+myElmOpts = defElmOptions { urlPrefix = Static "https://httpbin.org" }
 
 
 data MessageBody = MessageBody
diff --git a/examples/giphy/generate.hs b/examples/giphy/generate.hs
--- a/examples/giphy/generate.hs
+++ b/examples/giphy/generate.hs
@@ -9,7 +9,7 @@
                                toElmDecoderSourceWith, toElmTypeSourceWith)
 import           GHC.Generics (Generic)
 import           Servant.API  ((:>), Get, JSON, QueryParam)
-import           Servant.Elm  (ElmOptions (..), ElmType, Proxy (Proxy),
+import           Servant.Elm  (ElmOptions (..), ElmType, Proxy (Proxy), UrlPrefix(Static),
                                defElmImports, defElmOptions,
                                generateElmForAPIWith)
 
@@ -40,7 +40,7 @@
 myElmOpts =
   defElmOptions
     { urlPrefix =
-        "http://api.giphy.com/v1/gifs"
+        Static "http://api.giphy.com/v1/gifs"
     , elmExportOptions =
         options
     }
diff --git a/servant-elm.cabal b/servant-elm.cabal
--- a/servant-elm.cabal
+++ b/servant-elm.cabal
@@ -1,5 +1,5 @@
 name:                servant-elm
-version:             0.3.0.1
+version:             0.4.0.0
 synopsis:            Automatically derive Elm functions to query servant webservices.
 description:         Please see README.md
 homepage:            http://github.com/mattjbray/servant-elm#readme
diff --git a/src/Servant/Elm.hs b/src/Servant/Elm.hs
--- a/src/Servant/Elm.hs
+++ b/src/Servant/Elm.hs
@@ -15,6 +15,7 @@
        ( generateElmForAPI
        , generateElmForAPIWith
        , ElmOptions(..)
+       , UrlPrefix(..)
        , defElmOptions
        , defElmImports
        -- * Convenience re-exports from the "Elm" module
@@ -25,8 +26,8 @@
        , Proxy(Proxy)
        ) where
 
-import           Servant.Elm.Internal.Generate (ElmOptions (..), defElmImports,
-                                                defElmOptions,
+import           Servant.Elm.Internal.Generate (ElmOptions (..), UrlPrefix (..),
+                                                defElmImports, defElmOptions,
                                                 generateElmForAPI,
                                                 generateElmForAPIWith)
 
diff --git a/src/Servant/Elm/Internal/Generate.hs b/src/Servant/Elm/Internal/Generate.hs
--- a/src/Servant/Elm/Internal/Generate.hs
+++ b/src/Servant/Elm/Internal/Generate.hs
@@ -28,9 +28,12 @@
   { {- | The protocol, host and any path prefix to be used as the base for all
     requests.
 
-    Example: @"https://mydomain.com/api/v1"@
+    Example: @Static "https://mydomain.com/api/v1"@
+
+    When @Dynamic@, the generated Elm functions take the base URL as the first
+    argument.
     -}
-    urlPrefix             :: T.Text
+    urlPrefix             :: UrlPrefix
   , elmExportOptions      :: Elm.Options
     -- ^ Options to pass to elm-export
   , emptyResponseElmTypes :: [ElmDatatype]
@@ -40,13 +43,18 @@
   }
 
 
+data UrlPrefix
+  = Static T.Text
+  | Dynamic
+
+
 {-|
 Default options for generating Elm code.
 
 The default options are:
 
 > { urlPrefix =
->     ""
+>     Static ""
 > , elmExportOptions =
 >     Elm.defaultOptions
 > , emptyResponseElmTypes =
@@ -57,7 +65,7 @@
 -}
 defElmOptions :: ElmOptions
 defElmOptions = ElmOptions
-  { urlPrefix = ""
+  { urlPrefix = Static ""
   , elmExportOptions = Elm.defaultOptions
   , emptyResponseElmTypes =
       [ Elm.toElmType NoContent
@@ -65,6 +73,7 @@
       ]
   , stringElmTypes =
       [ Elm.toElmType ("" :: String)
+      , Elm.toElmType ("" :: T.Text)
       ]
   }
 
@@ -156,7 +165,7 @@
       mkTypeSignature opts request
 
     args =
-      mkArgs request
+      mkArgs opts request
 
     letParams =
       mkLetParams opts request
@@ -168,12 +177,19 @@
 mkTypeSignature :: ElmOptions -> F.Req ElmDatatype -> Doc
 mkTypeSignature opts request =
   (hsep . punctuate " ->" . concat)
-    [ headerTypes
+    [ catMaybes [urlPrefixType]
+    , headerTypes
     , urlCaptureTypes
     , queryTypes
     , catMaybes [bodyType, returnType]
     ]
   where
+    urlPrefixType :: Maybe Doc
+    urlPrefixType =
+        case (urlPrefix opts) of
+          Dynamic -> Just "String"
+          Static _ -> Nothing
+
     elmTypeRef :: ElmDatatype -> Doc
     elmTypeRef eType =
       stext (Elm.toElmTypeRefWith (elmExportOptions opts) eType)
@@ -238,11 +254,16 @@
 
 
 mkArgs
-  :: F.Req ElmDatatype
+  :: ElmOptions
+  -> F.Req ElmDatatype
   -> Doc
-mkArgs request =
+mkArgs opts request =
   (hsep . concat) $
-    [ -- Headers
+    [ -- Dynamic url prefix
+      case urlPrefix opts of
+        Dynamic -> ["urlBase"]
+        Static _ -> []
+    , -- Headers
       [ elmHeaderArg header
       | header <- request ^. F.reqHeaders
       ]
@@ -286,7 +307,7 @@
                 "toString >> "
           in
               name <$>
-              indent 4 ("|> Maybe.map" <+> parens (toStringSrc <> "Http.encodeUri >> (++)" <+> dquotes (name <> equals)) <$>
+              indent 4 ("|> Maybe.map" <+> parens (toStringSrc <> "Http.encodeUri >> (++)" <+> dquotes (elmName <> equals)) <$>
                         "|> Maybe.withDefault" <+> dquotes empty)
 
         F.Flag ->
@@ -300,8 +321,8 @@
             indent 4 ("|> List.map" <+> parens (backslash <> "val ->" <+> dquotes (name <> "[]=") <+> "++ (val |> toString |> Http.encodeUri)") <$>
                       "|> String.join" <+> dquotes "&")
       where
-        name =
-          elmQueryArg qarg
+        name = elmQueryArg qarg
+        elmName= qarg ^. F.queryArgName . F.argName . to (stext . F.unPathSegment)
 
 
 mkRequest :: ElmOptions -> F.Req ElmDatatype -> Doc
@@ -382,8 +403,10 @@
 mkUrl opts segments =
   "String.join" <+> dquotes "/" <$>
   (indent i . elmList)
-    ( dquotes (stext (urlPrefix opts))
-    : map segmentToDoc segments)
+    ( case urlPrefix opts of
+        Dynamic -> "urlBase"
+        Static url -> dquotes (stext url)
+      : map segmentToDoc segments)
   where
 
     segmentToDoc :: F.Segment ElmDatatype -> Doc
diff --git a/test/Common.hs b/test/Common.hs
--- a/test/Common.hs
+++ b/test/Common.hs
@@ -3,6 +3,7 @@
 {-# LANGUAGE TypeOperators #-}
 module Common where
 
+import           Data.Text    (Text)
 import           Data.Aeson   (ToJSON)
 import           Data.Proxy   (Proxy(Proxy))
 import           Elm          (ElmType)
@@ -28,7 +29,7 @@
          :> Capture "id" Int
          :> Get '[JSON] Book
   :<|> "books"
-         :> Capture "title" String
+         :> Capture "title" Text
          :> Get '[JSON] Book
   :<|> "books"
          :> QueryFlag "published"
diff --git a/test/GenerateSpec.hs b/test/GenerateSpec.hs
--- a/test/GenerateSpec.hs
+++ b/test/GenerateSpec.hs
@@ -12,11 +12,12 @@
 import           Data.Text                 (Text)
 import qualified Data.Text                 as T
 import qualified Data.Text.IO              as T
+import           Servant.API               ((:>), Get, JSON)
 import           Servant.Elm
 import           Test.Hspec                (Spec, describe, hspec, it)
 import           Test.HUnit                (Assertion, assertBool)
 
-import Common (testApi)
+import           Common                    (testApi)
 
 
 main :: IO ()
@@ -64,6 +65,25 @@
                               "import Http\n" <>
                               "import Json.Decode exposing (..)\n\n\n")]
                   let generated = map (<> "\n") (generateElmForAPI testApi)
+                  generated `itemsShouldBe` expected
+           it "with dynamic URLs" $
+               do expected <-
+                      mapM
+                          (\(fpath,header) -> do
+                               source <- T.readFile fpath
+                               return (fpath, header, source))
+                          [ ( "test/elm-sources/getOneWithDynamicUrlSource.elm"
+                            , "module GetOneWithDynamicUrlSource exposing (..)\n\n" <>
+                              "import Http\n" <>
+                              "import Json.Decode exposing (..)\n\n\n")]
+                  let generated =
+                          map
+                              (<> "\n")
+                              (generateElmForAPIWith
+                                   (defElmOptions
+                                    { urlPrefix = Dynamic
+                                    })
+                                   (Proxy :: Proxy ("one" :> Get '[JSON] Int)))
                   generated `itemsShouldBe` expected
 
 itemsShouldBe :: [Text] -> [(String, Text, Text)] -> IO ()
diff --git a/test/elm-sources/getBooksSource.elm b/test/elm-sources/getBooksSource.elm
--- a/test/elm-sources/getBooksSource.elm
+++ b/test/elm-sources/getBooksSource.elm
@@ -14,10 +14,10 @@
                   else
                     ""
                 , query_sort
-                    |> Maybe.map (Http.encodeUri >> (++) "query_sort=")
+                    |> Maybe.map (Http.encodeUri >> (++) "sort=")
                     |> Maybe.withDefault ""
                 , query_year
-                    |> Maybe.map (toString >> Http.encodeUri >> (++) "query_year=")
+                    |> Maybe.map (toString >> Http.encodeUri >> (++) "year=")
                     |> Maybe.withDefault ""
                 , query_filters
                     |> List.map (\val -> "query_filters[]=" ++ (val |> toString |> Http.encodeUri))
diff --git a/test/elm-sources/getOneWithDynamicUrlSource.elm b/test/elm-sources/getOneWithDynamicUrlSource.elm
new file mode 100644
--- /dev/null
+++ b/test/elm-sources/getOneWithDynamicUrlSource.elm
@@ -0,0 +1,27 @@
+module GetOneWithDynamicUrlSource exposing (..)
+
+import Http
+import Json.Decode exposing (..)
+
+
+getOne : String -> Http.Request (Int)
+getOne urlBase =
+    Http.request
+        { method =
+            "GET"
+        , headers =
+            []
+        , url =
+            String.join "/"
+                [ urlBase
+                , "one"
+                ]
+        , body =
+            Http.emptyBody
+        , expect =
+            Http.expectJson int
+        , timeout =
+            Nothing
+        , withCredentials =
+            False
+        }