diff --git a/cabal-install/cabal-install.cabal b/cabal-install/cabal-install.cabal
index 647c066ae33346f95471d2c86dd2bb76082ca15a..954644b8a03ef3193e20a605bebf9502529193a5 100644
--- a/cabal-install/cabal-install.cabal
+++ b/cabal-install/cabal-install.cabal
@@ -203,6 +203,7 @@ Test-Suite unit-tests
         tasty,
         tasty-hunit,
         tasty-quickcheck,
+        tagged,
         QuickCheck >= 2.5
 
   if flag(old-directory)
diff --git a/cabal-install/tests/UnitTests/Distribution/Client/Dependency/Modular/Solver.hs b/cabal-install/tests/UnitTests/Distribution/Client/Dependency/Modular/Solver.hs
index b82d6ff29fc144e678eb5630aab91dff90a0c3e0..9619f897fd492915977f9a283549df8007bdb8c9 100644
--- a/cabal-install/tests/UnitTests/Distribution/Client/Dependency/Modular/Solver.hs
+++ b/cabal-install/tests/UnitTests/Distribution/Client/Dependency/Modular/Solver.hs
@@ -7,6 +7,7 @@ module UnitTests.Distribution.Client.Dependency.Modular.Solver (tests, options)
 import Control.Monad
 import Data.Maybe (catMaybes, isNothing)
 import Data.Either (partitionEithers)
+import Data.Proxy
 import Data.Typeable
 import Data.Version
 import qualified Data.Map as Map