diff --git a/common/flatpak-oci-registry.c b/common/flatpak-oci-registry.c
index c1a1b174..7badf2ab 100644
--- a/common/flatpak-oci-registry.c
+++ b/common/flatpak-oci-registry.c
@@ -579,9 +579,18 @@ flatpak_oci_registry_initable_init (GInitable    *initable,
   FlatpakOciRegistry *self = FLATPAK_OCI_REGISTRY (initable);
   gboolean res;
 
-  if (self->tmp_dfd == -1 &&
-      !glnx_opendirat (AT_FDCWD, "/var/tmp", TRUE, &self->tmp_dfd, error))
-    return FALSE;
+  if (self->tmp_dfd == -1)
+    {
+      /* We don't use TMPDIR because the downloaded artifacts can be
+       * very big, and we want to prefer /var/tmp to /tmp.
+       */
+      const char *tmpdir = g_getenv ("FLATPAK_DOWNLOAD_TMPDIR");
+      if (tmpdir == NULL)
+        tmpdir = "/var/tmp";
+
+      if (!glnx_opendirat (AT_FDCWD, tmpdir, TRUE, &self->tmp_dfd, error))
+        return FALSE;
+    }
 
   if (g_str_has_prefix (self->uri, "file:/"))
     res = flatpak_oci_registry_ensure_local (self, self->for_write, cancellable, error);