diff --git a/Cabal-syntax/src/Distribution/Types/Executable.hs b/Cabal-syntax/src/Distribution/Types/Executable.hs
index 5362d7122b0..bf70702f41c 100644
--- a/Cabal-syntax/src/Distribution/Types/Executable.hs
+++ b/Cabal-syntax/src/Distribution/Types/Executable.hs
@@ -41,7 +41,7 @@ instance Semigroup Executable where
   a <> b =
     Executable
       { exeName = combineNames a b exeName "executable"
-      , modulePath = combine modulePath
+      , modulePath = combineNames a b modulePath "modulePath"
       , exeScope = combine exeScope
       , buildInfo = combine buildInfo
       }
diff --git a/Cabal-syntax/src/Distribution/Types/ForeignLib.hs b/Cabal-syntax/src/Distribution/Types/ForeignLib.hs
index 7e31a6cc7c0..19336af203d 100644
--- a/Cabal-syntax/src/Distribution/Types/ForeignLib.hs
+++ b/Cabal-syntax/src/Distribution/Types/ForeignLib.hs
@@ -28,6 +28,7 @@ import Distribution.Types.ForeignLibType
 import Distribution.Types.UnqualComponentName
 import Distribution.Version
 
+import Data.Monoid
 import qualified Distribution.Compat.CharParsing as P
 import qualified Text.PrettyPrint as Disp
 import qualified Text.Read as Read
@@ -144,13 +145,14 @@ instance Semigroup ForeignLib where
       , foreignLibType = combine foreignLibType
       , foreignLibOptions = combine foreignLibOptions
       , foreignLibBuildInfo = combine foreignLibBuildInfo
-      , foreignLibVersionInfo = combine'' foreignLibVersionInfo
-      , foreignLibVersionLinux = combine'' foreignLibVersionLinux
+      , foreignLibVersionInfo = chooseLast foreignLibVersionInfo
+      , foreignLibVersionLinux = chooseLast foreignLibVersionLinux
       , foreignLibModDefFile = combine foreignLibModDefFile
       }
     where
       combine field = field a `mappend` field b
-      combine'' field = field b
+      -- chooseLast: the second field overrides the first, unless it is Nothing
+      chooseLast field = getLast (Last (field a) <> Last (field b))
 
 instance Monoid ForeignLib where
   mempty =
diff --git a/Cabal-syntax/src/Distribution/Types/UnqualComponentName.hs b/Cabal-syntax/src/Distribution/Types/UnqualComponentName.hs
index 93feff2fbbe..3879cdd2169 100644
--- a/Cabal-syntax/src/Distribution/Types/UnqualComponentName.hs
+++ b/Cabal-syntax/src/Distribution/Types/UnqualComponentName.hs
@@ -14,7 +14,6 @@ module Distribution.Types.UnqualComponentName
 
 import Distribution.Compat.Prelude
 import Distribution.Utils.ShortText
-import Prelude as P (null)
 
 import Distribution.Parsec
 import Distribution.Pretty
@@ -111,28 +110,29 @@ unqualComponentNameToPackageName = mkPackageNameST . unUnqualComponentNameST
 -- (partial function).
 -- Useful in 'Semigroup' and similar instances.
 combineNames
-  :: a
+  :: (Monoid b, Eq b, Show b)
+  => a
   -> a
-  -> (a -> UnqualComponentName)
+  -> (a -> b)
   -> String
-  -> UnqualComponentName
+  -> b
 combineNames a b tacc tt
   -- One empty or the same.
-  | P.null unb
-      || una == unb =
+  | nb == mempty
+      || na == nb =
       na
-  | P.null una = nb
+  | na == mempty =
+      nb
   -- Both non-empty, different.
   | otherwise =
       error $
         "Ambiguous values for "
           ++ tt
           ++ " field: '"
-          ++ una
+          ++ show na
           ++ "' and '"
-          ++ unb
+          ++ show nb
           ++ "'"
   where
     (na, nb) = (tacc a, tacc b)
-    una = unUnqualComponentName na
-    unb = unUnqualComponentName nb
+{-# INLINEABLE combineNames #-}