diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,5 +1,13 @@
 # Changelog for horizon-spec
 
+## v0.6.3
+
+* Add `mkSubdir` splice function.
+
+## v0.6.2
+
+* Add `IsString` instances to Text types.
+
 ## v0.6.1
 
 * Re-export MkModifiers constructor.
diff --git a/horizon-spec.cabal b/horizon-spec.cabal
--- a/horizon-spec.cabal
+++ b/horizon-spec.cabal
@@ -1,6 +1,6 @@
 cabal-version:      3.0
 name:               horizon-spec
-version:            0.6.1
+version:            0.6.3
 synopsis:           Horizon Stable Package Set Type Definitions
 description:
   This package contains the type definitions for the Horizon stable package set (https://horizon-haskell.net). This is a schema used to define package sets sourcing from hackage and git.
@@ -52,7 +52,9 @@
     , dhall
     , path
     , path-dhall-instance
+    , template-haskell
     , text
+    , th-lift
 
   default-language:   Haskell2010
 
diff --git a/src/Horizon/Spec.hs b/src/Horizon/Spec.hs
--- a/src/Horizon/Spec.hs
+++ b/src/Horizon/Spec.hs
@@ -1,5 +1,6 @@
 {-# LANGUAGE DeriveAnyClass        #-}
 {-# LANGUAGE DuplicateRecordFields #-}
+{-# LANGUAGE TemplateHaskell       #-}
 module Horizon.Spec
   ( CabalFlag(MkCabalFlag)
   , Compiler(MkCompiler, fromCompiler)
@@ -23,44 +24,53 @@
   , Repo(MkRepo, fromRepo)
   , Revision(MkRevision, fromRevision)
   , Subdir(MkSubdir, fromSubdir)
+  , mkSubdir
   , TarballSource(MkTarballSource, fromTarballSource)
   , Url(MkUrl, fromUrl)
   , Version (MkVersion, fromVersion)
   )
   where
 
-import           Data.Kind  (Type)
-import           Data.Map   (Map)
-import           Data.Text  (Text)
-import           Dhall      (FromDhall, Generic, ToDhall)
-import           Path       (Dir, File, Path, Rel)
-import           Path.Dhall ()
+import           Data.Kind                (Type)
+import           Data.Map                 (Map)
+import           Data.String              (IsString)
+import           Data.Text                (Text)
+import           Dhall                    (FromDhall, Generic, ToDhall)
+import           Language.Haskell.TH      (Exp, Q)
+import           Language.Haskell.TH.Lift (deriveLift, lift)
+import           Path                     (Dir, File, Path, Rel, parseRelDir)
+import           Path.Dhall               ()
 
 
 type Url :: Type
 newtype Url = MkUrl { fromUrl :: Text }
   deriving stock (Eq, Show)
-  deriving newtype (FromDhall, ToDhall)
+  deriving newtype (FromDhall, ToDhall, IsString)
 
 type Repo :: Type
 newtype Repo = MkRepo { fromRepo :: Url }
   deriving stock (Eq, Show)
-  deriving newtype (FromDhall, ToDhall)
+  deriving newtype (FromDhall, ToDhall, IsString)
 
 type Subdir :: Type
 newtype Subdir = MkSubdir { fromSubdir :: Path Rel Dir }
   deriving stock (Eq, Show)
   deriving newtype (FromDhall, ToDhall)
 
+$(deriveLift 'MkSubdir)
+
+mkSubdir :: FilePath -> Q Exp
+mkSubdir = either (error . show) (lift . MkSubdir) . parseRelDir
+
 type Name :: Type
 newtype Name = MkName { fromName :: Text }
   deriving stock (Eq, Ord, Show)
-  deriving newtype (FromDhall, ToDhall)
+  deriving newtype (FromDhall, ToDhall, IsString)
 
 type Version :: Type
 newtype Version = MkVersion { fromVersion :: Text }
   deriving stock (Eq, Show)
-  deriving newtype (FromDhall, ToDhall)
+  deriving newtype (FromDhall, ToDhall, IsString)
 
 type GitSource :: Type
 data GitSource where
@@ -132,7 +142,7 @@
 newtype Revision where
   MkRevision :: { fromRevision :: Text } -> Revision
   deriving stock (Show, Eq, Generic)
-  deriving newtype (FromDhall, ToDhall)
+  deriving newtype (FromDhall, ToDhall, IsString)
 
 type Compiler :: Type
 newtype Compiler where