diff --git a/.rubocop_todo.yml b/.rubocop_todo.yml
index a3b80f141..900bb8201 100644
--- a/.rubocop_todo.yml
+++ b/.rubocop_todo.yml
@@ -371,14 +371,6 @@ Performance/StartWith:
   Exclude:
     - 'app/lib/extractor.rb'
 
-# This cop supports unsafe autocorrection (--autocorrect-all).
-# Configuration parameters: OnlySumOrWithInitialValue.
-Performance/Sum:
-  Exclude:
-    - 'app/lib/activity_tracker.rb'
-    - 'app/models/trends/history.rb'
-    - 'lib/paperclip/color_extractor.rb'
-
 # This cop supports unsafe autocorrection (--autocorrect-all).
 Performance/TimesMap:
   Exclude:
diff --git a/app/lib/activity_tracker.rb b/app/lib/activity_tracker.rb
index 8829d8605..9160ef22a 100644
--- a/app/lib/activity_tracker.rb
+++ b/app/lib/activity_tracker.rb
@@ -43,7 +43,7 @@ class ActivityTracker
 
     case @type
     when :basic
-      redis.mget(*keys).map(&:to_i).sum
+      redis.mget(*keys).sum(&:to_i)
     when :unique
       redis.pfcount(*keys)
     end
diff --git a/app/models/trends/history.rb b/app/models/trends/history.rb
index 83532e7bc..db3689933 100644
--- a/app/models/trends/history.rb
+++ b/app/models/trends/history.rb
@@ -11,7 +11,7 @@ class Trends::History
     end
 
     def uses
-      with_redis { |redis| redis.mget(*@days.map { |day| day.key_for(:uses) }).map(&:to_i).sum }
+      with_redis { |redis| redis.mget(*@days.map { |day| day.key_for(:uses) }).sum(&:to_i) }
     end
 
     def accounts
diff --git a/lib/paperclip/color_extractor.rb b/lib/paperclip/color_extractor.rb
index 2e8dc04fd..19529fb8a 100644
--- a/lib/paperclip/color_extractor.rb
+++ b/lib/paperclip/color_extractor.rb
@@ -173,7 +173,7 @@ module Paperclip
     def palette_from_histogram(result, quantity)
       frequencies       = result.scan(/([0-9]+)\:/).flatten.map(&:to_f)
       hex_values        = result.scan(/\#([0-9A-Fa-f]{6,8})/).flatten
-      total_frequencies = frequencies.reduce(&:+).to_f
+      total_frequencies = frequencies.sum.to_f
 
       frequencies.map.with_index { |f, i| [f / total_frequencies, hex_values[i]] }
                  .sort_by { |r| -r[0] }