diff --git a/guix/utils.scm b/guix/utils.scm
index c68094cf49b43e9f2d2163b2dc04d9a618428c00..ded31142aab2741c3dd99e1c6eacc2ecb0fc3c02 100644
--- a/guix/utils.scm
+++ b/guix/utils.scm
@@ -369,7 +369,7 @@ (define (default-keyword-arguments args defaults)
     (match defaults
       ((kw value rest ...)
        (loop rest
-             (if (assoc-ref kw args)
+             (if (memq kw args)
                  args
                  (cons* kw value args))))
       (()
diff --git a/tests/utils.scm b/tests/utils.scm
index 6590ed91cf8cca567f31a286adc74ab9dc37fe37..960928c842f36fe0a16f771922a683db078d9764 100644
--- a/tests/utils.scm
+++ b/tests/utils.scm
@@ -111,6 +111,18 @@ (define temp-file
         (ensure-keyword-arguments '(#:foo 2) '(#:bar 3))
         (ensure-keyword-arguments '(#:foo 2) '(#:bar 3 #:foo 42))))
 
+(test-equal "default-keyword-arguments"
+  '((#:foo 2)
+    (#:foo 2)
+    (#:foo 2 #:bar 3)
+    (#:foo 2 #:bar 3)
+    (#:foo 2 #:bar 3))
+  (list (default-keyword-arguments '() '(#:foo 2))
+        (default-keyword-arguments '(#:foo 2) '(#:foo 4))
+        (default-keyword-arguments '() '(#:bar 3 #:foo 2))
+        (default-keyword-arguments '(#:bar 3) '(#:foo 2))
+        (default-keyword-arguments '(#:foo 2 #:bar 3) '(#:bar 6))))
+
 (test-assert "filtered-port, file"
   (let* ((file  (search-path %load-path "guix.scm"))
          (input (open-file file "r0b")))