diff --git a/guix/profiles.scm b/guix/profiles.scm
index 33a0511a3a..5c19c95d42 100644
--- a/guix/profiles.scm
+++ b/guix/profiles.scm
@@ -512,7 +512,8 @@ entries of MANIFEST, or #f if MANIFEST does not have any GHC packages."
         (system* (string-append #+ghc "/bin/ghc-pkg") "init" db-dir)
         (for-each copy-conf-file
                   (append-map conf-files
-                              '#$(manifest-inputs manifest)))
+                              (delete-duplicates
+                               '#$(manifest-inputs manifest))))
         (let ((success
                (zero?
                 (system* (string-append #+ghc "/bin/ghc-pkg") "recache"