diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5a24156..c91fec5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,12 @@
 ## HEAD
 
+## 4.0.12
+
+- Fix deadlock when a single process kills the same app twice (https://github.com/heroku/hatchet/pull/63)
+- Add ability to debug deadlock with HATCHET_DEBUG_DEADLOCK env var.
+
+## 4.0.11
+
 - Fix logic in rake task (https://github.com/heroku/hatchet/pull/62)
 
 ## 4.0.10
diff --git a/lib/hatchet.rb b/lib/hatchet.rb
index 98e40d3..892c529 100644
--- a/lib/hatchet.rb
+++ b/lib/hatchet.rb
@@ -31,4 +31,13 @@ def self.git_branch
     raise "Attempting to find current branch name. Error: Cannot describe git: #{out}" unless $?.success?
     out
   end
-end
\ No newline at end of file
+
+  if ENV["HATCHET_DEBUG_DEADLOCK"]
+    Thread.new do
+      loop do
+        sleep ENV["HATCHET_DEBUG_DEADLOCK"].to_f # seconds
+        Thread.list.each { |t| puts "=" * 80; puts t.backtrace }
+      end
+    end
+  end
+end
diff --git a/lib/hatchet/reaper.rb b/lib/hatchet/reaper.rb
index 1c678e5..d3fd483 100644
--- a/lib/hatchet/reaper.rb
+++ b/lib/hatchet/reaper.rb
@@ -52,6 +52,7 @@ def cycle
       body = e.response.body
       if body =~ /Couldn\'t find that app./
         puts "#{@message}, but looks like it was already deleted"
+        mutex.close # ensure only gets called on block exit and not on `retry`
         retry
       end
       raise e
diff --git a/lib/hatchet/version.rb b/lib/hatchet/version.rb
index 9adec30..627b13e 100644
--- a/lib/hatchet/version.rb
+++ b/lib/hatchet/version.rb
@@ -1,3 +1,3 @@
 module Hatchet
-  VERSION = "4.0.11"
+  VERSION = "4.0.12"
 end