diff --git a/lib/ably/modules/ably.rb b/lib/ably/modules/ably.rb
index 0cb5ef9a..e67f7905 100644
--- a/lib/ably/modules/ably.rb
+++ b/lib/ably/modules/ably.rb
@@ -8,7 +8,7 @@ module Ably
   # network failures either at the client, between the client and Ably, within an Ably data center, or at the IO domain registrar
   # see https://ably.com/docs/client-lib-development-guide/features/#RSC15a
   #
-  FALLBACK_DOMAIN = 'ably-realtime.com'.freeze
+  FALLBACK_DOMAIN = 'ably-realtime-nonprod.com'.freeze
   FALLBACK_IDS = %w(a b c d e).freeze
 
   # Default production fallbacks a.ably-realtime.com ... e.ably-realtime.com
diff --git a/lib/ably/rest/client.rb b/lib/ably/rest/client.rb
index 3dbda2df..d9e162ee 100644
--- a/lib/ably/rest/client.rb
+++ b/lib/ably/rest/client.rb
@@ -214,7 +214,7 @@ def initialize(options)
         when custom_host || options[:realtime_host] || custom_port || custom_tls_port
           []
         when environment
-          CUSTOM_ENVIRONMENT_FALLBACKS_SUFFIXES.map { |host| "#{environment}#{host}" }
+          CUSTOM_ENVIRONMENT_FALLBACKS_SUFFIXES.map { |host| "#{environment.sub(/-dev$/, '')}#{host}" }
         else
           Ably::FALLBACK_HOSTS
         end
diff --git a/spec/acceptance/realtime/connection_failures_spec.rb b/spec/acceptance/realtime/connection_failures_spec.rb
index 6afb7616..c34043e0 100644
--- a/spec/acceptance/realtime/connection_failures_spec.rb
+++ b/spec/acceptance/realtime/connection_failures_spec.rb
@@ -1469,7 +1469,7 @@ def kill_connection_transport_and_prevent_valid_resume
       end
 
       context 'with non-production environment' do
-        let(:environment)    { 'sandbox' }
+        let(:environment)    { 'lmars-dev' }
         let(:expected_host)  { "#{environment}-#{Ably::Realtime::Client::DOMAIN}" }
         let(:client_options) { timeout_options.merge(environment: environment) }
 
diff --git a/spec/acceptance/rest/auth_spec.rb b/spec/acceptance/rest/auth_spec.rb
index ef07af9f..72a46da4 100644
--- a/spec/acceptance/rest/auth_spec.rb
+++ b/spec/acceptance/rest/auth_spec.rb
@@ -1300,14 +1300,14 @@ def coerce_if_time_value(field_name, value, params = {})
       end
 
       context 'when the JWT embeds an Ably token' do
-        let(:token) { Faraday.post(auth_url, { keyName: key_name, keySecret: key_secret, jwtType: :embedded }).body }
+        let(:token) { Faraday.post(auth_url, { environment: environment, keyName: key_name, keySecret: key_secret, jwtType: :embedded }).body }
 
         it 'authenticates correctly using the embedded token' do
           expect(client.stats).to_not be_nil()
         end
 
         context 'and the requested token is encrypted' do
-          let(:token) { Faraday.post(auth_url, { keyName: key_name, keySecret: key_secret, jwtType: :embedded, encrypted: 1 }).body }
+          let(:token) { Faraday.post(auth_url, { environment: environment, keyName: key_name, keySecret: key_secret, jwtType: :embedded, encrypted: 1 }).body }
 
           it 'authenticates correctly using the embedded token' do
             expect(client.stats).to_not be_nil()
diff --git a/spec/acceptance/rest/client_spec.rb b/spec/acceptance/rest/client_spec.rb
index e1619c6e..1a1b835d 100644
--- a/spec/acceptance/rest/client_spec.rb
+++ b/spec/acceptance/rest/client_spec.rb
@@ -312,7 +312,7 @@ def encode64(text)
 
       context 'when environment is NOT production (#RSC15b)' do
         context 'and custom fallback hosts are empty' do
-          let(:client_options) { default_options.merge(environment: 'sandbox', key: api_key, fallback_hosts: []) }
+          let(:client_options) { default_options.merge(environment: 'lmars-dev', key: api_key, fallback_hosts: []) }
           let!(:default_host_request_stub) do
             stub_request(:post, "https://#{environment}-#{Ably::Rest::Client::DOMAIN}#{path}").to_return do
               raise Faraday::TimeoutError.new('timeout error message')
@@ -325,14 +325,14 @@ def encode64(text)
         end
 
         context 'and no custom fallback hosts are provided' do
-          let(:client_options) { default_options.merge(environment: 'sandbox', key: api_key) }
+          let(:client_options) { default_options.merge(environment: 'lmars-dev', key: api_key) }
 
-          it 'should make connection attempts to sandbox-a-fallback.ably-realtime.com, sandbox-b-fallback.ably-realtime.com, sandbox-c-fallback.ably-realtime.com, sandbox-d-fallback.ably-realtime.com, sandbox-e-fallback.ably-realtime.com (#RSC15a)' do
+          it 'should make connection attempts to lmars-dev-a-fallback.ably-realtime.com, lmars-dev-b-fallback.ably-realtime.com, lmars-dev-c-fallback.ably-realtime.com, lmars-dev-d-fallback.ably-realtime.com, lmars-dev-e-fallback.ably-realtime.com (#RSC15a)' do
             hosts = []
             5.times do
               hosts << client.fallback_connection.host
             end
-            expect(hosts).to match_array(%w(a b c d e).map { |id| "sandbox-#{id}-fallback.ably-realtime.com" })
+            expect(hosts).to match_array(%w(a b c d e).map { |id| "lmars-dev-#{id}-fallback.ably-realtime.com" })
           end
         end
       end
diff --git a/spec/rspec_config.rb b/spec/rspec_config.rb
index c299da4a..b3c92ffb 100644
--- a/spec/rspec_config.rb
+++ b/spec/rspec_config.rb
@@ -35,7 +35,7 @@
       key_name: 'app_id.key_name',
       key_secret: 'secret',
       api_key: 'app_id.key_name:secret',
-      environment: 'sandbox'
+      environment: 'lmars-dev'
     ))
     WebMock.enable!
   end
diff --git a/spec/shared/client_initializer_behaviour.rb b/spec/shared/client_initializer_behaviour.rb
index 84ff2df4..bfe64cdf 100644
--- a/spec/shared/client_initializer_behaviour.rb
+++ b/spec/shared/client_initializer_behaviour.rb
@@ -164,10 +164,10 @@ def rest?
       end
 
       context 'with environment option' do
-        let(:client_options) { default_options.merge(environment: 'sandbox', auto_connect: false) }
+        let(:client_options) { default_options.merge(environment: 'lmars-dev', auto_connect: false) }
 
         it 'uses an alternate endpoint' do
-          expect(subject.endpoint.to_s).to eql("#{protocol}s://sandbox-#{subdomain}.ably.io")
+          expect(subject.endpoint.to_s).to eql("#{protocol}s://lmars-dev-#{subdomain}.ably.io")
         end
       end
 
diff --git a/spec/support/test_app.rb b/spec/support/test_app.rb
index 2e7fc394..79986d36 100644
--- a/spec/support/test_app.rb
+++ b/spec/support/test_app.rb
@@ -66,7 +66,7 @@ def delete
   end
 
   def environment
-    ENV['ABLY_ENV'] || 'sandbox'
+    ENV['ABLY_ENV'] || 'lmars-dev'
   end
 
   def create_test_app