diff --git a/test/configuration.nix b/test/configuration.nix
index 79eefab..5724ec4 100644
--- a/test/configuration.nix
+++ b/test/configuration.nix
@@ -95,6 +95,9 @@
     ];
   };
 
+  # Disk image is too small for some tests:
+  boot.tmp.useTmpfs = true;
+
   environment.hakurei = {
     enable = true;
     stateDir = "/var/lib/hakurei";