diff --git a/elm-package.cabal b/elm-package.cabal
--- a/elm-package.cabal
+++ b/elm-package.cabal
@@ -1,5 +1,5 @@
 Name: elm-package
-Version: 0.2
+Version: 0.2.1
 
 Synopsis:
     Package manager for Elm libraries
@@ -66,7 +66,7 @@
         elm-compiler >= 0.14 && < 0.15,
         filepath >= 1 && < 2.0,
         HTTP >= 4000.2.5 && < 4000.3,
-        http-client >= 0.3 && < 0.4,
+        http-client >= 0.3 && < 0.5,
         http-client-tls >= 0.2 && < 0.3,
         http-types >= 0.7 && < 0.9,
         mtl >= 2 && < 3,
@@ -128,12 +128,12 @@
         elm-compiler >= 0.14 && < 0.15,
         filepath >= 1 && < 2.0,
         HTTP >= 4000.2.5 && < 4000.3,
-        http-client >= 0.3 && < 0.4,
+        http-client >= 0.3 && < 0.5,
         http-client-tls >= 0.2 && < 0.3,
         http-types >= 0.7 && < 0.9,
         mtl >= 2 && < 3,
         network >= 2.4 && < 2.7,
-        optparse-applicative >= 0.8.1 && < 0.11,
+        optparse-applicative >= 0.11 && < 0.12,
         pretty,
         process >= 1 && < 2,
         text,
diff --git a/src/CommandLine/Arguments.hs b/src/CommandLine/Arguments.hs
--- a/src/CommandLine/Arguments.hs
+++ b/src/CommandLine/Arguments.hs
@@ -1,7 +1,9 @@
 module CommandLine.Arguments (parse) where
 
 import Control.Applicative (pure, optional, (<$>), (<*>), (<|>))
+import Control.Monad (mzero)
 import Control.Monad.Error (throwError)
+import Control.Monad.Reader.Class (ask)
 import Data.Monoid ((<>), mconcat, mempty)
 import Data.Version (showVersion)
 import qualified Options.Applicative as Opt
@@ -160,9 +162,14 @@
 
 -- ARGUMENT PARSERS
 
+mkParser :: (String -> Maybe a) -> Opt.ReadM a
+mkParser p =
+  do  s <- Opt.str
+      maybe mzero return . p $ s
+
 package :: Opt.Parser N.Name
 package =
-    Opt.argument N.fromString $
+    Opt.argument (mkParser N.fromString) $
         mconcat
         [ Opt.metavar "PACKAGE"
         , Opt.help "A specific package name (e.g. evancz/automaton)"
@@ -170,7 +177,7 @@
 
 version :: Opt.Parser V.Version
 version =
-    Opt.argument V.fromString $
+    Opt.argument (mkParser V.fromString) $
         mconcat
         [ Opt.metavar "VERSION"
         , Opt.help "Specific version of a package (e.g. 1.2.0)"