diff --git a/dhall-docs/doctest/Main.hs b/dhall-docs/doctest/Main.hs
index eaac1d683..e01a50cb7 100644
--- a/dhall-docs/doctest/Main.hs
+++ b/dhall-docs/doctest/Main.hs
@@ -1,18 +1,23 @@
-module Main where
+module Main (main) where
 
 import System.FilePath ((</>))
 
 import qualified GHC.IO.Encoding
 import qualified System.Directory
+import qualified System.Environment
 import qualified System.IO
 import qualified Test.DocTest
 
 main :: IO ()
 main = do
     GHC.IO.Encoding.setLocaleEncoding System.IO.utf8
-    pwd    <- System.Directory.getCurrentDirectory
+    args <- System.Environment.getArgs
+    pwd <- System.Directory.getCurrentDirectory
     prefix <- System.Directory.makeAbsolute pwd
-    Test.DocTest.doctest
+    let src = prefix </> "src"
+
+    Test.DocTest.doctest $
         [ "--fast"
-        , prefix </> "src"
+        ] <> args <>
+        [ src
         ]
diff --git a/dhall-lsp-server/doctest/Main.hs b/dhall-lsp-server/doctest/Main.hs
index 20d594862..b858ae470 100644
--- a/dhall-lsp-server/doctest/Main.hs
+++ b/dhall-lsp-server/doctest/Main.hs
@@ -1,23 +1,26 @@
-module Main where
+module Main (main) where
 
 import System.FilePath ((</>))
 
 import qualified GHC.IO.Encoding
 import qualified System.Directory
+import qualified System.Environment
 import qualified System.IO
 import qualified Test.DocTest
 
 main :: IO ()
 main = do
-
     GHC.IO.Encoding.setLocaleEncoding System.IO.utf8
-    pwd    <- System.Directory.getCurrentDirectory
+    args <- System.Environment.getArgs
+    pwd <- System.Directory.getCurrentDirectory
     prefix <- System.Directory.makeAbsolute pwd
+    let src = prefix </> "src"
 
-    Test.DocTest.doctest
+    Test.DocTest.doctest $
         [ "--fast"
         , "-XOverloadedStrings"
         , "-XRecordWildCards"
-        , "-i" <> (prefix </> "src")
-        , prefix </> "src/Dhall/LSP/Backend/Diagnostics.hs"
+        ] <> args <>
+        [ "-i" <> src
+        , src </> "Dhall/LSP/Backend/Diagnostics.hs"
         ]
diff --git a/dhall-toml/doctest/Main.hs b/dhall-toml/doctest/Main.hs
index 225dcbcc1..6f968330a 100644
--- a/dhall-toml/doctest/Main.hs
+++ b/dhall-toml/doctest/Main.hs
@@ -1,14 +1,24 @@
-module Main where
+module Main (main) where
 
 import System.FilePath ((</>))
 
+import qualified GHC.IO.Encoding
 import qualified System.Directory
+import qualified System.Environment
+import qualified System.IO
 import qualified Test.DocTest
 
 main :: IO ()
 main = do
+    GHC.IO.Encoding.setLocaleEncoding System.IO.utf8
+    args <- System.Environment.getArgs
     pwd <- System.Directory.getCurrentDirectory
     prefix <- System.Directory.makeAbsolute pwd
     let src = prefix </> "src"
-    Test.DocTest.doctest [ "--fast",  "-i" <> src, src ]
 
+    Test.DocTest.doctest $
+        [ "--fast"
+        ] <> args <>
+        [  "-i" <> src
+        , src
+        ]
diff --git a/dhall/doctest/Main.hs b/dhall/doctest/Main.hs
index d6d4ac57f..053d79411 100644
--- a/dhall/doctest/Main.hs
+++ b/dhall/doctest/Main.hs
@@ -1,6 +1,6 @@
 {-# LANGUAGE CPP #-}
 
-module Main where
+module Main (main) where
 
 import System.FilePath ((</>))
 
@@ -13,10 +13,11 @@ import qualified Test.Mockery.Directory
 
 main :: IO ()
 main = do
-
     GHC.IO.Encoding.setLocaleEncoding System.IO.utf8
-    pwd    <- System.Directory.getCurrentDirectory
+    args <- System.Environment.getArgs
+    pwd <- System.Directory.getCurrentDirectory
     prefix <- System.Directory.makeAbsolute pwd
+    let src = prefix </> "src"
 
     System.Environment.setEnv "XDG_CACHE_HOME" (pwd </> ".cache")
 
@@ -34,11 +35,12 @@ main = do
           , "in  { name = \"Simon\", favoriteFont = Font.`Comic Sans` } : Person"
           ]
 
-        Test.DocTest.doctest
+        Test.DocTest.doctest $
             [ "-DWITH_HTTP"
             , "-DUSE_HTTP_CLIENT_TLS"
             , "--fast"
-            , prefix </> "ghc-src"
+            ] <> args <>
+            [ prefix </> "ghc-src"
 
             -- Unfortunately we cannot target the entire @src@ directory.
             -- The reason is that src/Dhall/Version.hs depends on
@@ -47,11 +49,11 @@ main = do
             -- Instead, we target a selection of modules whose combined module
             -- dependency tree covers all modules that contain doctests.
 
-            -- , prefix </> "src"
-            , "-i" <> (prefix </> "src")
+            -- , src
+            , "-i" <> src
 #if __GLASGOW_HASKELL__ >= 806
-            , prefix </> "src/Dhall/Deriving.hs"
+            , src </> "Dhall/Deriving.hs"
 #endif
-            , prefix </> "src/Dhall/Tags.hs"
-            , prefix </> "src/Dhall/Tutorial.hs"
+            , src </> "Dhall/Tags.hs"
+            , src </> "Dhall/Tutorial.hs"
             ]