diff --git a/modules/openapi-generator/src/main/resources/ruby-client/configuration.mustache b/modules/openapi-generator/src/main/resources/ruby-client/configuration.mustache
index 64bf69b157da..0745df86f712 100644
--- a/modules/openapi-generator/src/main/resources/ruby-client/configuration.mustache
+++ b/modules/openapi-generator/src/main/resources/ruby-client/configuration.mustache
@@ -171,7 +171,7 @@ module {{moduleName}}
 
     # Returns base URL for specified operation based on server settings
     def base_url(operation = nil)
-      index = server_operation_index[operation]
+      index = server_operation_index.fetch(operation, server_index)
       return "#{scheme}://#{[host, base_path].join('/').gsub(/\/+/, '/')}".sub(/\/+\z/, '') if index == nil
 
       server_url(index, server_operation_variables.fetch(operation, server_variables), operation_server_settings[operation])
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/configuration.rb b/samples/client/petstore/ruby-autoload/lib/petstore/configuration.rb
index 94c3d78226fc..8a7e83b68d57 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/configuration.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/configuration.rb
@@ -200,7 +200,7 @@ def base_path=(base_path)
 
     # Returns base URL for specified operation based on server settings
     def base_url(operation = nil)
-      index = server_operation_index[operation]
+      index = server_operation_index.fetch(operation, server_index)
       return "#{scheme}://#{[host, base_path].join('/').gsub(/\/+/, '/')}".sub(/\/+\z/, '') if index == nil
 
       server_url(index, server_operation_variables.fetch(operation, server_variables), operation_server_settings[operation])
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/configuration.rb b/samples/client/petstore/ruby-faraday/lib/petstore/configuration.rb
index 611ec7f50fe2..19d20a3d7e97 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/configuration.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/configuration.rb
@@ -204,7 +204,7 @@ def base_path=(base_path)
 
     # Returns base URL for specified operation based on server settings
     def base_url(operation = nil)
-      index = server_operation_index[operation]
+      index = server_operation_index.fetch(operation, server_index)
       return "#{scheme}://#{[host, base_path].join('/').gsub(/\/+/, '/')}".sub(/\/+\z/, '') if index == nil
 
       server_url(index, server_operation_variables.fetch(operation, server_variables), operation_server_settings[operation])
diff --git a/samples/client/petstore/ruby/lib/petstore/configuration.rb b/samples/client/petstore/ruby/lib/petstore/configuration.rb
index 94c3d78226fc..8a7e83b68d57 100644
--- a/samples/client/petstore/ruby/lib/petstore/configuration.rb
+++ b/samples/client/petstore/ruby/lib/petstore/configuration.rb
@@ -200,7 +200,7 @@ def base_path=(base_path)
 
     # Returns base URL for specified operation based on server settings
     def base_url(operation = nil)
-      index = server_operation_index[operation]
+      index = server_operation_index.fetch(operation, server_index)
       return "#{scheme}://#{[host, base_path].join('/').gsub(/\/+/, '/')}".sub(/\/+\z/, '') if index == nil
 
       server_url(index, server_operation_variables.fetch(operation, server_variables), operation_server_settings[operation])
diff --git a/samples/openapi3/client/extensions/x-auth-id-alias/ruby-client/lib/x_auth_id_alias/configuration.rb b/samples/openapi3/client/extensions/x-auth-id-alias/ruby-client/lib/x_auth_id_alias/configuration.rb
index b3841dfb55e0..79482f9351fb 100644
--- a/samples/openapi3/client/extensions/x-auth-id-alias/ruby-client/lib/x_auth_id_alias/configuration.rb
+++ b/samples/openapi3/client/extensions/x-auth-id-alias/ruby-client/lib/x_auth_id_alias/configuration.rb
@@ -200,7 +200,7 @@ def base_path=(base_path)
 
     # Returns base URL for specified operation based on server settings
     def base_url(operation = nil)
-      index = server_operation_index[operation]
+      index = server_operation_index.fetch(operation, server_index)
       return "#{scheme}://#{[host, base_path].join('/').gsub(/\/+/, '/')}".sub(/\/+\z/, '') if index == nil
 
       server_url(index, server_operation_variables.fetch(operation, server_variables), operation_server_settings[operation])
diff --git a/samples/openapi3/client/features/dynamic-servers/ruby/lib/dynamic_servers/configuration.rb b/samples/openapi3/client/features/dynamic-servers/ruby/lib/dynamic_servers/configuration.rb
index 1f09fc659e9b..a949c7d71299 100644
--- a/samples/openapi3/client/features/dynamic-servers/ruby/lib/dynamic_servers/configuration.rb
+++ b/samples/openapi3/client/features/dynamic-servers/ruby/lib/dynamic_servers/configuration.rb
@@ -200,7 +200,7 @@ def base_path=(base_path)
 
     # Returns base URL for specified operation based on server settings
     def base_url(operation = nil)
-      index = server_operation_index[operation]
+      index = server_operation_index.fetch(operation, server_index)
       return "#{scheme}://#{[host, base_path].join('/').gsub(/\/+/, '/')}".sub(/\/+\z/, '') if index == nil
 
       server_url(index, server_operation_variables.fetch(operation, server_variables), operation_server_settings[operation])
diff --git a/samples/openapi3/client/features/generate-alias-as-model/ruby-client/lib/petstore/configuration.rb b/samples/openapi3/client/features/generate-alias-as-model/ruby-client/lib/petstore/configuration.rb
index e662f0ce4466..34e950886b62 100644
--- a/samples/openapi3/client/features/generate-alias-as-model/ruby-client/lib/petstore/configuration.rb
+++ b/samples/openapi3/client/features/generate-alias-as-model/ruby-client/lib/petstore/configuration.rb
@@ -200,7 +200,7 @@ def base_path=(base_path)
 
     # Returns base URL for specified operation based on server settings
     def base_url(operation = nil)
-      index = server_operation_index[operation]
+      index = server_operation_index.fetch(operation, server_index)
       return "#{scheme}://#{[host, base_path].join('/').gsub(/\/+/, '/')}".sub(/\/+\z/, '') if index == nil
 
       server_url(index, server_operation_variables.fetch(operation, server_variables), operation_server_settings[operation])