diff --git a/app/models/comment.rb b/app/models/comment.rb
index 649de1d..e9dd5a6 100644
--- a/app/models/comment.rb
+++ b/app/models/comment.rb
@@ -2,12 +2,25 @@ class Comment
   include Mongoid::Document
   include Mongoid::Timestamps
 
+  after_create :increase_counter_cache
+  before_destroy :decrease_counter_cache
+
   field :body, :type => String
   index :user_id
 
-  belongs_to :err
+  belongs_to :err, :class_name => "Problem"
   belongs_to :user
 
   validates_presence_of :body
+
+  protected
+    def increase_counter_cache
+      err.inc(:comments_count, 1)
+    end
+
+    def decrease_counter_cache
+      err.inc(:comments_count, -1) if err
+    end
+
 end
 
diff --git a/app/models/problem.rb b/app/models/problem.rb
index fb4760a..b3fb752 100644
--- a/app/models/problem.rb
+++ b/app/models/problem.rb
@@ -21,6 +21,7 @@ class Problem
   field :user_agents, :type => Array, :default => []
   field :messages, :type => Array, :default => []
   field :hosts, :type => Array, :default => []
+  field :comments_count, :type => Integer, :default => 0
 
   index :app_id
   index :app_name
diff --git a/app/views/errs/_table.html.haml b/app/views/errs/_table.html.haml
index d6dbb55..51095ad 100644
--- a/app/views/errs/_table.html.haml
+++ b/app/views/errs/_table.html.haml
@@ -26,7 +26,7 @@
           %td.message
             = link_to trucated_err_message(problem), app_err_path(problem.app, problem)
             %em= problem.where
-            - if problem.comments.any?
+            - if problem.comments_count > 0
               - comment = problem.comments.last
               %br
               .inline_comment
diff --git a/db/migrate/20111019163257_add_problem_comments_count.rb b/db/migrate/20111019163257_add_problem_comments_count.rb
new file mode 100644
index 0000000..c9f724b
--- /dev/null
+++ b/db/migrate/20111019163257_add_problem_comments_count.rb
@@ -0,0 +1,10 @@
+class AddProblemCommentsCount < Mongoid::Migration
+  def self.up
+    Problem.all.each do |problem|
+      problem.update_attributes(:comments_count => problem.comments.count)
+    end
+  end
+
+  def self.down
+  end
+end
\ No newline at end of file
diff --git a/spec/factories/comment_factories.rb b/spec/factories/comment_factories.rb
index 1bee372..23e27f4 100644
--- a/spec/factories/comment_factories.rb
+++ b/spec/factories/comment_factories.rb
@@ -1,5 +1,6 @@
 Factory.define :comment do |c|
   c.user       {|u| u.association :user}
   c.body       'Test comment'
+  c.err        {|e| e.association :problem}
 end
 
diff --git a/spec/models/problem_spec.rb b/spec/models/problem_spec.rb
index e26b6c8..096d39f 100644
--- a/spec/models/problem_spec.rb
+++ b/spec/models/problem_spec.rb
@@ -276,5 +276,31 @@ describe Problem do
     end
   end
 
+  context "comment counter cache" do
+    before do
+      @app = Factory(:app)
+      @problem = Factory(:problem, :app => @app)
+    end
+
+    it "#comments_count returns 0 by default" do
+      @problem.comments_count.should == 0
+    end
+
+    it "adding a comment increases #comments_count by 1" do
+      lambda {
+        Factory(:comment, :err => @problem)
+      }.should change(@problem, :comments_count).from(0).to(1)
+    end
+
+    it "removing a comment decreases #comments_count by 1" do
+      comment1 = Factory(:comment, :err => @problem)
+      lambda {
+        @problem.reload.comments.first.destroy
+        @problem.reload
+      }.should change(@problem, :comments_count).from(1).to(0)
+    end
+  end
+
+
 end
 
--
libgit2 0.21.2