diff --git a/guix-data-service/jobs/load-new-guix-revision.scm b/guix-data-service/jobs/load-new-guix-revision.scm
index e684ea0..1deef87 100644
--- a/guix-data-service/jobs/load-new-guix-revision.scm
+++ b/guix-data-service/jobs/load-new-guix-revision.scm
@@ -854,7 +854,14 @@ WHERE job_id = $1")
                  (expt 2. 20))))
 
      (format (current-error-port)
-             "inferior heap size: ~a MiB~%"
+             "inferior heap: ~a MiB used (~a MiB heap)~%"
+             (round
+              (/ (inferior-eval
+                  '(let ((stats (gc-stats)))
+                     (- (assoc-ref stats 'heap-size)
+                        (assoc-ref stats 'heap-free-size)))
+                  inf)
+                 (expt 2. 20)))
              (round
               (/ (inferior-eval '(assoc-ref (gc-stats) 'heap-size) inf)
                  (expt 2. 20))))