diff --git a/app/models/issue.rb b/app/models/issue.rb
index b4113b9fe..39b4c2dbf 100644
--- a/app/models/issue.rb
+++ b/app/models/issue.rb
@@ -1243,12 +1243,26 @@ class Issue < ApplicationRecord
 
   # Preloads visible total spent time for a collection of issues
   def self.load_visible_total_spent_hours(issues, user=User.current)
-    if issues.any?
+    return if issues.empty?
+
+    # For leaf issues, `total_spent_hours` equals `spent_hours`, so reuse
+    # the preloaded visible spent hours to avoid the expensive query below.
+    optimizable_leaf_issues, remaining_issues = issues.partition do |issue|
+      issue.leaf? &&
+        issue.instance_variable_defined?(:@spent_hours) &&
+        !issue.instance_variable_get(:@spent_hours).nil?
+    end
+
+    optimizable_leaf_issues.each do |issue|
+      issue.instance_variable_set :@total_spent_hours, issue.spent_hours
+    end
+
+    if remaining_issues.any?
       hours_by_issue_id = TimeEntry.visible(user).joins(:issue).
         joins("JOIN #{Issue.table_name} parent ON parent.root_id = #{Issue.table_name}.root_id" +
           " AND parent.lft <= #{Issue.table_name}.lft AND parent.rgt >= #{Issue.table_name}.rgt").
-        where("parent.id IN (?)", issues.map(&:id)).group("parent.id").sum(:hours)
-      issues.each do |issue|
+        where("parent.id IN (?)", remaining_issues.map(&:id)).group("parent.id").sum(:hours)
+      remaining_issues.each do |issue|
         issue.instance_variable_set :@total_spent_hours, (hours_by_issue_id[issue.id] || 0.0)
       end
     end
diff --git a/test/unit/issue_test.rb b/test/unit/issue_test.rb
index a5c0bbb87..77c2a3a91 100644
--- a/test/unit/issue_test.rb
+++ b/test/unit/issue_test.rb
@@ -222,6 +222,18 @@ class IssueTest < ActiveSupport::TestCase
     assert_include 'Parent task is invalid', issue.errors.full_messages
   end
 
+  def test_load_visible_total_spent_hours_should_use_loaded_spent_hours_for_leaf_issues
+    issue = Issue.find(1)
+    assert issue.leaf?
+    # preloaded visible spent hours value is stored in @spent_hours instance variable
+    issue.instance_variable_set(:@spent_hours, 3.5)
+    TimeEntry.expects(:visible).never
+
+    Issue.load_visible_total_spent_hours([issue])
+
+    assert_equal 3.5, issue.instance_variable_get(:@total_spent_hours)
+  end
+
   def assert_visibility_match(user, issues)
     assert_equal issues.collect(&:id).sort, Issue.all.select {|issue| issue.visible?(user)}.collect(&:id).sort
   end