diff --git a/guix-data-service/jobs/load-new-guix-revision.scm b/guix-data-service/jobs/load-new-guix-revision.scm
index 1412392..ddfd364 100644
--- a/guix-data-service/jobs/load-new-guix-revision.scm
+++ b/guix-data-service/jobs/load-new-guix-revision.scm
@@ -50,7 +50,7 @@
   #:use-module (guix serialization)
   #:use-module (guix build utils)
   #:use-module ((guix build syscalls)
-                #:select (set-thread-name))
+                #:select (set-thread-name free-disk-space))
   #:use-module (guix-data-service config)
   #:use-module (guix-data-service database)
   #:use-module (guix-data-service utils)
@@ -1761,14 +1761,19 @@ SELECT 1 FROM derivation_source_file_nars WHERE derivation_source_file_id = $1"
 
   (define (call-with-inferior proc)
     (define (check-wal-size)
-      (define threshold (* 4096 (expt 2 20)))
-
       (define (get-wal-bytes)
         (catch #t
           (lambda ()
             (stat:size (stat "/var/guix/db/db.sqlite-wal")))
           (lambda _ 0)))
 
+      (define threshold
+        (max
+         (* 4096 (expt 2 20))
+         (* 0.8
+            (- (free-disk-space "/var/guix/db/db.sqlite-wal")
+               (get-wal-bytes)))))
+
       (if (< (get-wal-bytes) threshold)
           #t
           (let loop ((wal-bytes (get-wal-bytes)))