diff --git a/guix-data-service/database.scm b/guix-data-service/database.scm
index 88d1172..1f4e13a 100644
--- a/guix-data-service/database.scm
+++ b/guix-data-service/database.scm
@@ -306,7 +306,7 @@
         (lambda (col-i)
           (let ((val (result-get-value result-ptr row-i col-i)))
             (cond
-             ((eq? #f val) '())
+             ((eq? #f val) NULL)
              ((string-null? val)
               (if (eq? 1 (%PQgetisnull
                           (squee/unwrap-result-ptr result-ptr) row-i col-i))