diff --git a/lib/collector.rb b/lib/collector.rb
index 9c44c60..04a47b1 100644
--- a/lib/collector.rb
+++ b/lib/collector.rb
@@ -4,7 +4,7 @@ class Collector
 	class PrefixProxy
 		attr_reader :prometheus, :prefix
 		def initialize prometheus, prefix
-			@prometheus, @prefix = prometheus, prefix
+			@prometheus, @prefix = prometheus, prefix.dup.freeze
 		end
 
 		def counter name, **options
@@ -22,6 +22,10 @@ class Collector
 		def summary name, **options
 			@prometheus.summary :"#{prefix}_#{name}", **options
 		end
+
+		def prefix_proxy prefix
+			PrefixProxy.new @prometheus, "#{@prefix}_#{prefix}"
+		end
 	end
 
 	def self.start prometheus: nil, journal: nil
@@ -32,6 +36,9 @@ class Collector
 		@settings = settings
 		@journal = journal || Systemd::Journal.new( flags: Systemd::Journal::Flags::SYSTEM_ONLY)
 		@prometheus = prometheus || Prometheus::Client.registry
+		def @prometheus.prefix_proxy prefix
+			PrefixProxy.new self, prefix
+		end
 		@store = {}
 
 		@errors     = @prometheus.counter :postfix_exporter_errors_total, docstring: 'Count internal errors/exceptions'
diff --git a/lib/collector/postfix.rb b/lib/collector/postfix.rb
index aef248e..ecc55b3 100644
--- a/lib/collector/postfix.rb
+++ b/lib/collector/postfix.rb
@@ -54,8 +54,8 @@ class Collector::Postfix
 	class Postscreen
 		def initialize store, prometheus
 			@store = store
-			@noqueue                 = Noqueue.new store, Collector::PrefixProxy.new( prometheus, :noqueue)
-			@cache                   = Cache.new store,   Collector::PrefixProxy.new( prometheus, :cache)
+			@noqueue                 = Noqueue.new store, prometheus.prefix_proxy( :noqueue)
+			@cache                   = Cache.new store,   prometheus.prefix_proxy( :cache)
 			@connect_from            = prometheus.counter :connect_from_total,       docstring: 'A counter of connections to postscreen'
 			@whitelisted             = prometheus.counter :whitelisted_total,        docstring: 'A counter of WHITELISTED connections to postscreen'
 			@pass_old                = prometheus.counter :pass_old_total,           docstring: 'A counter of PASS OLD connections to postscreen'
@@ -181,7 +181,7 @@ class Collector::Postfix
 	class Smtpd
 		def initialize store, prometheus
 			@store = store
-			@noqueue                    = Noqueue.new store, Collector::PrefixProxy.new( prometheus, :noqueue)
+			@noqueue                    = Noqueue.new store, prometheus.prefix_proxy( :noqueue)
 			@connect_from               = prometheus.counter :connect_from_total, docstring: 'A counter of connections to smtpd', labels: %i[from_unknown]
 			%w[0 1].each {|x| @connect_from.increment by: 0, labels: {from_unknown: x} }
 			@tls                        = prometheus.counter :tls_total, docstring: 'A counter of TLS connections to smtpd with TLS-version and cipher', labels: %i[trust tls cipher]
@@ -330,7 +330,7 @@ class Collector::Postfix
 	class Verify
 		def initialize store, prometheus
 			@store = store
-			@cache = Cache.new store, Collector::PrefixProxy.new( prometheus, :cache)
+			@cache = Cache.new store, prometheus.prefix_proxy( :cache)
 		end
 
 		def collect entry
@@ -344,13 +344,14 @@ class Collector::Postfix
 
 	def initialize store, prometheus
 		@store = store
-		@postscreen = Postscreen.new store, Collector::PrefixProxy.new( prometheus, :postscreen)
-		@smtp       = Smtp.new       store, Collector::PrefixProxy.new( prometheus, :smtp)
-		@smtpd      = Smtpd.new      store, Collector::PrefixProxy.new( prometheus, :smtpd)
-		@submission = Smtpd.new      store, Collector::PrefixProxy.new( prometheus, :submission)
-		@tlsproxy   = Tlsproxy.new   store, Collector::PrefixProxy.new( prometheus, :tlsproxy)
-		@scache     = SCache.new     store, Collector::PrefixProxy.new( prometheus, :scache)
-		@bounce     = Bounce.new     store, Collector::PrefixProxy.new( prometheus, :bounce)
+		@postscreen = Postscreen.new store, prometheus.prefix_proxy( :postscreen)
+		@smtp       = Smtp.new       store, prometheus.prefix_proxy( :smtp)
+		@smtpd      = Smtpd.new      store, prometheus.prefix_proxy( :smtpd)
+		@submission = Smtpd.new      store, prometheus.prefix_proxy( :submission)
+		@tlsproxy   = Tlsproxy.new   store, prometheus.prefix_proxy( :tlsproxy)
+		@scache     = SCache.new     store, prometheus.prefix_proxy( :scache)
+		@bounce     = Bounce.new     store, prometheus.prefix_proxy( :bounce)
+		@verify     = Verify.new     store, prometheus.prefix_proxy( :verify)
 		@qmgr       = prometheus.counter :qmgr_total,     docstring: 'A counter of qmgr actions'
 		@cleanup    = prometheus.counter :cleanup_total,  docstring: 'A counter of cleanup actions'
 		@lmtp       = prometheus.counter :lmtp_total,     docstring: 'A counter of ltmp actions'