diff --git a/lib/rackstash/logger.rb b/lib/rackstash/logger.rb
index 5f82514..1dff721 100644
--- a/lib/rackstash/logger.rb
+++ b/lib/rackstash/logger.rb
@@ -3,6 +3,7 @@
 # This software may be modified and distributed under the terms
 # of the MIT license. See the LICENSE.txt file for details.
 
+require 'concurrent'
 require 'forwardable'
 
 require 'rackstash/buffer_stack'
@@ -51,6 +52,8 @@ module Rackstash
       @level = DEBUG
       @progname = PROGNAME
       @formatter = Formatter.new
+
+      @buffer_stack = Concurrent::ThreadLocalVar.new
     end
 
     # Set the base log level as either one of the {SEVERITIES} or a
@@ -239,7 +242,7 @@ module Rackstash
     private
 
     def buffer_stack
-      @buffer_stack ||= Rackstash::BufferStack.new(@sink)
+      @buffer_stack.value ||= BufferStack.new(@sink)
     end
 
     def buffer
diff --git a/spec/rackstash/logger_spec.rb b/spec/rackstash/logger_spec.rb
index 733eac9..8a5135e 100644
--- a/spec/rackstash/logger_spec.rb
+++ b/spec/rackstash/logger_spec.rb
@@ -321,4 +321,18 @@ describe Rackstash::Logger do
       expect(messages.last).to include message: 'Unknown', severity: 5
     end
   end
+
+  context 'with multiple threads' do
+    it 'maintains thread-local stacks' do
+      first_stack = logger.send(:buffer_stack)
+      expect(first_stack).to be_a Rackstash::BufferStack
+
+      Thread.new do
+        second_stack = logger.send(:buffer_stack)
+        expect(second_stack).to be_a Rackstash::BufferStack
+
+        expect(second_stack).to_not eql first_stack
+      end.join
+    end
+  end
 end