diff --git a/build-aux/hydra/gnu-system.scm b/build-aux/hydra/gnu-system.scm
index c612ff1f12..8d9b43c0b0 100644
--- a/build-aux/hydra/gnu-system.scm
+++ b/build-aux/hydra/gnu-system.scm
@@ -159,7 +159,7 @@ (define MiB
                        (set-guile-for-build (default-guile))
                        (system-disk-image installation-os
                                           #:disk-image-size
-                                          (* 850 MiB))))))
+                                          (* 860 MiB))))))
       '()))
 
 (define (tarball-jobs store system)