diff --git a/guix/derivations.scm b/guix/derivations.scm
index 92d50503ce..eb94fea55e 100644
--- a/guix/derivations.scm
+++ b/guix/derivations.scm
@@ -239,12 +239,17 @@ the store."
   "Return a list of inputs, such that when INPUTS contains the same DRV twice,
 they are coalesced, with their sub-derivations merged.  This is needed because
 Nix itself keeps only one of them."
+  (define (derivation-file-name* obj)
+    (if (derivation? obj)
+        (derivation-file-name obj)
+        obj))
+
   (fold (lambda (input result)
           (match input
-            (($ <derivation-input> (= derivation-file-name path) sub-drvs)
+            (($ <derivation-input> (= derivation-file-name* path) sub-drvs)
              ;; XXX: quadratic
              (match (find (match-lambda
-                            (($ <derivation-input> (= derivation-file-name p)
+                            (($ <derivation-input> (= derivation-file-name* p)
                                                    s)
                              (string=? p path)))
                           result)
@@ -685,7 +690,7 @@ name of each input with that input's hash."
                              (make-derivation-input hash sub-drvs))))
                         inputs)))
        (make-derivation outputs
-                        (sort inputs
+                        (sort (coalesce-duplicate-inputs inputs)
                               (lambda (drv1 drv2)
                                 (string<? (derivation-input-derivation drv1)
                                           (derivation-input-derivation drv2))))