diff --git a/.rubocop.yml b/.rubocop.yml
index 004a921e4d..6dea6df645 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -142,6 +142,8 @@ Performance/StringIdentifierArgument: # new in 1.13
   Enabled: true
 Performance/StringInclude: # new in 1.7
   Enabled: true
+Performance/Sum: # new in 1.8
+  Enabled: true
 
 
 # Old cops
diff --git a/.rubocop_todo.yml b/.rubocop_todo.yml
index 571a646edf..ce86c030a3 100644
--- a/.rubocop_todo.yml
+++ b/.rubocop_todo.yml
@@ -63,13 +63,6 @@ Minitest/EmptyLineBeforeAssertionMethods:
     - 'test/new_relic/agent_test.rb'
     - 'test/new_relic/cli/commands/deployments_test.rb'
 
-# Offense count: 1
-# This cop supports unsafe autocorrection (--autocorrect-all).
-# Configuration parameters: OnlySumOrWithInitialValue.
-Performance/Sum:
-  Exclude:
-    - 'lib/new_relic/agent/system_info.rb'
-
 # Offense count: 72
 # This cop supports unsafe autocorrection (--autocorrect-all).
 Performance/UnfreezeString:
diff --git a/lib/new_relic/agent/system_info.rb b/lib/new_relic/agent/system_info.rb
index 5080ac574a..fe63184dda 100644
--- a/lib/new_relic/agent/system_info.rb
+++ b/lib/new_relic/agent/system_info.rb
@@ -128,7 +128,7 @@ def self.parse_cpuinfo(cpuinfo)
 
         num_physical_packages = cores.keys.map(&:first).uniq.size
         num_physical_cores = cores.size
-        num_logical_processors = cores.values.reduce(0, :+)
+        num_logical_processors = cores.values.sum
 
         if num_physical_cores == 0
           num_logical_processors = total_processors