diff --git a/lib/prometheus/client/rack/collector.rb b/lib/prometheus/client/rack/collector.rb
index c85ca4d6..d359dbde 100644
--- a/lib/prometheus/client/rack/collector.rb
+++ b/lib/prometheus/client/rack/collector.rb
@@ -39,11 +39,11 @@ def init_request_metrics
             :http_requests_total,
             'A counter of the total number of HTTP requests made.')
           @requests_duration = @registry.counter(
-            :http_request_durations_total_microseconds,
+            :http_request_duration_total_microseconds,
             'The total amount of time spent answering HTTP requests ' \
             '(microseconds).')
           @durations = @registry.summary(
-            :http_request_durations_microseconds,
+            :http_request_duration_microseconds,
             'A histogram of the response latency (microseconds).')
         end
 
diff --git a/spec/examples/metric_example.rb b/spec/examples/metric_example.rb
index 6fc5aed8..02d5f3aa 100644
--- a/spec/examples/metric_example.rb
+++ b/spec/examples/metric_example.rb
@@ -12,7 +12,7 @@
       exception = Prometheus::Client::LabelSetValidator::ReservedLabelError
 
       expect do
-        described_class.new(:foo, 'foo docstring',  __name__: 'reserved')
+        described_class.new(:foo, 'foo docstring', __name__: 'reserved')
       end.to raise_exception exception
     end
 
diff --git a/spec/prometheus/client/formats/text_spec.rb b/spec/prometheus/client/formats/text_spec.rb
index d149e936..891a9168 100644
--- a/spec/prometheus/client/formats/text_spec.rb
+++ b/spec/prometheus/client/formats/text_spec.rb
@@ -4,7 +4,7 @@
 
 describe Prometheus::Client::Formats::Text do
   let(:summary_value) do
-    { 0.5  => 4.2, 0.9  => 8.32, 0.99 => 15.3 }.tap do |value|
+    { 0.5 => 4.2, 0.9 => 8.32, 0.99 => 15.3 }.tap do |value|
       allow(value).to receive_messages(sum: 1243.21, total: 93)
     end
   end
diff --git a/spec/prometheus/client/rack/collector_spec.rb b/spec/prometheus/client/rack/collector_spec.rb
index dce7bc21..0ba779cf 100644
--- a/spec/prometheus/client/rack/collector_spec.rb
+++ b/spec/prometheus/client/rack/collector_spec.rb
@@ -42,8 +42,8 @@
 
     {
       http_requests_total: 1,
-      http_request_durations_total_microseconds: 2,
-      http_request_durations_microseconds: { 0.5 => 2, 0.9 => 2, 0.99 => 2 },
+      http_request_duration_total_microseconds: 2,
+      http_request_duration_microseconds: { 0.5 => 2, 0.9 => 2, 0.99 => 2 },
     }.each do |metric, result|
       expect(registry.get(metric).get(labels)).to eql(result)
     end