diff --git a/services/www.spec b/services/www.spec
index 4362cdb..d0a4ec1 100644
--- a/services/www.spec
+++ b/services/www.spec
@@ -1,5 +1,6 @@
 command: echo "coucou"
 consumes: www
+requires-domain: true
 
 %directory ${SERVICE_ROOT}/
 	name: data directory
diff --git a/src/service.cr b/src/service.cr
index 3acfbc1..23da9ae 100644
--- a/src/service.cr
+++ b/src/service.cr
@@ -44,6 +44,7 @@ commands = CommandsList.new
 
 commands.push "add", "Adds a service to an environment." do |args|
 	providers = Hash(String, String).new
+	domain = nil
 
 	environment, service = Service.parse_id args[0]
 
@@ -52,15 +53,25 @@ commands.push "add", "Adds a service to an environment." do |args|
 
 		match = arg.match /(.*)=(.*)/
 
-		if match.nil?
+		if match.nil? || match.size < 2
 			raise ::Service::Exception.new "usage: service add <service> <token=provider>"
 			next
 		end
 
-		providers[match[1]] = match[2]
+		_, key, value = match
+
+		if key == "domain"
+			domain = value
+		else
+			providers[key] = value
+		end
 	end
 
 	Service.new(service, environment).tap do |service|
+		if domain
+			service.domain = domain
+		end
+
 		service.consumes.each do |token|
 			provider = providers[token.token]?
 
@@ -76,7 +87,10 @@ commands.push "add", "Adds a service to an environment." do |args|
 
 			service.providers[token.token] = provider
 		end
-		pp! service.providers
+
+		if service.requires_domain && !service.domain
+			raise Service::Exception.new "'#{service.name}' requires a domain= parameter to be provided!"
+		end
 	end.write RC_DIRECTORY
 end
 
diff --git a/src/service/service.cr b/src/service/service.cr
index b8813f1..dac4699 100644
--- a/src/service/service.cr
+++ b/src/service/service.cr
@@ -19,7 +19,7 @@ class Service
 	getter environment : Environment
 	getter providers = ProvidersList.new
 
-	getter domain : String?
+	property domain : String?
 
 	# The place we’ll store configuration and data.
 	@root : String?
@@ -81,6 +81,10 @@ class Service
 			file << "root: #{@root}"
 		end
 
+		if @domain
+			file << "domain: #{@domain}"
+		end
+
 		@providers.each do |token, provider|
 			file << "%consumes #{token}"
 			file << "    from: #{provider}"
@@ -120,6 +124,9 @@ class Service
 	def consumes
 		@reference.consumes
 	end
+	def requires_domain
+		@reference.requires_domain
+	end
 
 	def root
 		@root || "#{@environment.root}/#{name}"
diff --git a/src/service/service_definition.cr b/src/service/service_definition.cr
index 2e53fb8..bf1e53e 100644
--- a/src/service/service_definition.cr
+++ b/src/service/service_definition.cr
@@ -49,6 +49,8 @@ class ServiceDefinition
 	getter pre_start_hooks : Array(Hook)
 	getter provides : Array(Provides)
 
+	getter requires_domain = false
+
 	def initialize(@name, specs : SpecParser)
 		sections = specs.sections
 		specs = specs.assignments
@@ -60,6 +62,18 @@ class ServiceDefinition
 		@consumes      = specs["consumes"]?.try &.as_a_or_s.map { |x| Consumes.new x } || Array(Consumes).new
 		@environment_variables = specs["environment-variables"]?.try &.as_a_or_s || Array(String).new
 
+		# FIXME: as_b?
+		requires_domain = specs["requires-domain"]?.try &.as_s
+		case requires_domain
+		when nil
+		when "true", "yes"
+			@requires_domain = true
+		when "false", "no"
+			@requires_domain = false
+		else
+			STDERR.puts "warning: definition '#{@name}' has a 'requires-domain' entry with an invalid value"
+		end
+
 		@pre_start_hooks = Array(Hook).new
 
 		sections.each do |section|