diff --git a/nixos/tests/consul.nix b/nixos/tests/consul.nix
index a5188d12830..eb7dd45923f 100644
--- a/nixos/tests/consul.nix
+++ b/nixos/tests/consul.nix
@@ -55,6 +55,7 @@ let
 
   server = index: { pkgs, ... }:
     let
+      numConsensusServers = builtins.length allConsensusServerHosts;
       thisConsensusServerHost = builtins.elemAt allConsensusServerHosts index;
       ip = thisConsensusServerHost; # since we already use IPs to identify servers
     in
@@ -71,12 +72,12 @@ let
             inherit webUi;
             extraConfig = defaultExtraConfig // {
               server = true;
-              bootstrap_expect = builtins.length allConsensusServerHosts;
+              bootstrap_expect = numConsensusServers;
               retry_join =
                 # If there's only 1 node in the network, we allow self-join;
                 # otherwise, the node must not try to join itself, and join only the other servers.
                 # See https://github.com/hashicorp/consul/issues/2868
-                if builtins.length allConsensusServerHosts == 1
+                if numConsensusServers == 1
                   then allConsensusServerHosts
                   else builtins.filter (h: h != thisConsensusServerHost) allConsensusServerHosts;
               bind_addr = ip;