diff --git a/logstash-core/lib/logstash/instrument/namespaced_metric.rb b/logstash-core/lib/logstash/instrument/namespaced_metric.rb
index 6b0ad020e..330ded453 100644
--- a/logstash-core/lib/logstash/instrument/namespaced_metric.rb
+++ b/logstash-core/lib/logstash/instrument/namespaced_metric.rb
@@ -45,7 +45,7 @@ module LogStash module Instrument
     end
 
     def namespace(name)
-      NamespacedMetric.new(metric, namespace_name.concat(Array(name)))
+      NamespacedMetric.new(metric, namespace_name + Array(name))
     end
 
     private
diff --git a/logstash-core/spec/logstash/instrument/namespaced_metric_spec.rb b/logstash-core/spec/logstash/instrument/namespaced_metric_spec.rb
index 6ba84168d..289a9dba5 100644
--- a/logstash-core/spec/logstash/instrument/namespaced_metric_spec.rb
+++ b/logstash-core/spec/logstash/instrument/namespaced_metric_spec.rb
@@ -22,4 +22,11 @@ describe LogStash::Instrument::NamespacedMetric do
   it "returns the value of the block" do
     expect(subject.time(:duration_ms) { "hello" }).to eq("hello")
   end
+
+  it "its doesnt change the original `namespace` when creating a subnamespace" do
+    new_namespace = subject.namespace(:wally)
+
+    expect(subject.namespace_name).to eq([namespace])
+    expect(new_namespace.namespace_name).to eq([:stats, :wally])
+  end
 end