diff --git a/spec/lib/rate_limiter_spec.rb b/spec/lib/rate_limiter_spec.rb
index 9947366bf8b..17247ccef48 100644
--- a/spec/lib/rate_limiter_spec.rb
+++ b/spec/lib/rate_limiter_spec.rb
@@ -105,7 +105,8 @@ describe RateLimiter do
 
     context 'handles readonly' do
       before do
-        Discourse.redis.without_namespace.slaveof '10.0.0.1', '99999'
+        # random IP address in the ULA range that does not exist
+        Discourse.redis.without_namespace.slaveof 'fdec:3f5d:d0b7:4c4b:472b:636a:4370:7ac5', '49999'
       end
 
       after do