postfix-exporter.gemspec in postfix-exporter-1.0.2 vs postfix-exporter.gemspec in postfix-exporter-2.0.1

@@ -21,10 +21,10 @@
 	s.files = `git ls-files -z`.split("\0").reject { |f| f =~ /^(G|spec|Rakefile)/ }
 	s.executables = ["postfix-exporter"]
 
 	s.required_ruby_version = ">= 2.1.0"
 
-	s.add_runtime_dependency 'prometheus-client'
+	s.add_runtime_dependency 'prometheus-client', '~> 0.7'
 	s.add_runtime_dependency 'rack'
 
 	s.add_development_dependency 'bundler'
 	s.add_development_dependency 'github-release'
 	s.add_development_dependency 'rake', '~> 10.4', '>= 10.4.2'