diff --git a/lib/concurrent/array.rb b/lib/concurrent/array.rb
index c83f3bb06..f3786056e 100644
--- a/lib/concurrent/array.rb
+++ b/lib/concurrent/array.rb
@@ -2,7 +2,8 @@
 require 'concurrent/thread_safe/util'
 
 module Concurrent
-  if Concurrent.on_cruby?
+  case
+  when Concurrent.on_cruby?
 
     # Because MRI never runs code in parallel, the existing
     # non-thread-safe structures should usually work fine.
@@ -21,10 +22,10 @@ module Concurrent
     #   may be lost. Use `#concat` instead.
     #
     #   @see http://ruby-doc.org/core-2.2.0/Array.html Ruby standard library `Array`
-    class Array < ::Array;
+    class Array < ::Array
     end
 
-  elsif Concurrent.on_jruby?
+  when Concurrent.on_jruby?
     require 'jruby/synchronized'
 
     # @!macro concurrent_array
@@ -32,15 +33,29 @@ class Array < ::Array
       include JRuby::Synchronized
     end
 
-  elsif Concurrent.on_rbx? || Concurrent.on_truffleruby?
+  when Concurrent.on_rbx?
     require 'monitor'
-    require 'concurrent/thread_safe/util/array_hash_rbx'
+    require 'concurrent/thread_safe/util/data_structures'
 
     # @!macro concurrent_array
     class Array < ::Array
     end
 
     ThreadSafe::Util.make_synchronized_on_rbx Concurrent::Array
+
+  when Concurrent.on_truffleruby?
+    require 'concurrent/thread_safe/util/data_structures'
+
+    # @!macro concurrent_array
+    class Array < ::Array
+    end
+
+    ThreadSafe::Util.make_synchronized_on_truffleruby Concurrent::Array
+
+  else
+    warn 'Possibly unsupported Ruby implementation'
+    class Array < ::Array
+    end
   end
 end
 
diff --git a/lib/concurrent/hash.rb b/lib/concurrent/hash.rb
index 9c952c1fb..3ecc2ff04 100644
--- a/lib/concurrent/hash.rb
+++ b/lib/concurrent/hash.rb
@@ -2,7 +2,8 @@
 require 'concurrent/thread_safe/util'
 
 module Concurrent
-  if Concurrent.on_cruby?
+  case
+  when Concurrent.on_cruby?
 
     # @!macro [attach] concurrent_hash
     #
@@ -12,10 +13,10 @@ module Concurrent
     #   which takes the lock repeatedly when reading an item.
     #
     #   @see http://ruby-doc.org/core-2.2.0/Hash.html Ruby standard library `Hash`
-    class Hash < ::Hash;
+    class Hash < ::Hash
     end
 
-  elsif Concurrent.on_jruby?
+  when Concurrent.on_jruby?
     require 'jruby/synchronized'
 
     # @!macro concurrent_hash
@@ -23,14 +24,30 @@ class Hash < ::Hash
       include JRuby::Synchronized
     end
 
-  elsif Concurrent.on_rbx? || Concurrent.on_truffleruby?
+  when Concurrent.on_rbx?
     require 'monitor'
-    require 'concurrent/thread_safe/util/array_hash_rbx'
+    require 'concurrent/thread_safe/util/data_structures'
 
     # @!macro concurrent_hash
     class Hash < ::Hash
     end
 
     ThreadSafe::Util.make_synchronized_on_rbx Concurrent::Hash
+
+  when Concurrent.on_truffleruby?
+    require 'concurrent/thread_safe/util/data_structures'
+
+    # @!macro concurrent_hash
+    class Hash < ::Hash
+    end
+
+    ThreadSafe::Util.make_synchronized_on_truffleruby Concurrent::Hash
+
+  else
+    warn 'Possibly unsupported Ruby implementation'
+    class Hash < ::Hash
+    end
+
   end
 end
+
diff --git a/lib/concurrent/set.rb b/lib/concurrent/set.rb
index 7e9956f29..8e72d9bb4 100644
--- a/lib/concurrent/set.rb
+++ b/lib/concurrent/set.rb
@@ -3,7 +3,8 @@
 require 'set'
 
 module Concurrent
-  if Concurrent.on_cruby?
+  case
+  when Concurrent.on_cruby?
 
     # Because MRI never runs code in parallel, the existing
     # non-thread-safe structures should usually work fine.
@@ -25,7 +26,7 @@ module Concurrent
     class Set < ::Set;
     end
 
-  elsif Concurrent.on_jruby?
+  when Concurrent.on_jruby?
     require 'jruby/synchronized'
 
     # @!macro concurrent_Set
@@ -33,15 +34,29 @@ class Set < ::Set
       include JRuby::Synchronized
     end
 
-  elsif Concurrent.on_rbx? || Concurrent.on_truffleruby?
+  when Concurrent.on_rbx?
     require 'monitor'
-    require 'concurrent/thread_safe/util/array_hash_rbx'
+    require 'concurrent/thread_safe/util/data_structures'
 
     # @!macro concurrent_Set
     class Set < ::Set
     end
 
-    ThreadSafe::Util.make_synchronized_on_rbx Set
+    ThreadSafe::Util.make_synchronized_on_rbx Concurrent::Set
+
+  when Concurrent.on_truffleruby?
+    require 'concurrent/thread_safe/util/data_structures'
+
+    # @!macro concurrent_array
+    class Set < ::Set
+    end
+
+    ThreadSafe::Util.make_synchronized_on_truffleruby Concurrent::Set
+
+  else
+    warn 'Possibly unsupported Ruby implementation'
+    class Set < ::Set
+    end
   end
 end
 
diff --git a/lib/concurrent/thread_safe/util/array_hash_rbx.rb b/lib/concurrent/thread_safe/util/data_structures.rb
similarity index 61%
rename from lib/concurrent/thread_safe/util/array_hash_rbx.rb
rename to lib/concurrent/thread_safe/util/data_structures.rb
index ee129efdf..e43d9c50a 100644
--- a/lib/concurrent/thread_safe/util/array_hash_rbx.rb
+++ b/lib/concurrent/thread_safe/util/data_structures.rb
@@ -6,23 +6,13 @@ module Util
       def self.make_synchronized_on_rbx(klass)
         klass.class_eval do
           private
+
           def _mon_initialize
             @_monitor = Monitor.new unless @_monitor # avoid double initialisation
           end
 
-          def initialize(*args)
-            _mon_initialize
-            super
-          end
-
-          def self.allocate
-            obj = super
-            obj.send(:_mon_initialize)
-            obj
-          end
-
-          def self.[](*args)
-            obj = super
+          def self.new(*args)
+            obj = super(*args)
             obj.send(:_mon_initialize)
             obj
           end
@@ -42,18 +32,24 @@ def #{method}(*args)
             klass.class_eval <<-RUBY, __FILE__, __LINE__ + 1
               def #{method}(*args)
                 monitor = @_monitor
-
-                unless monitor
-                  raise("BUG: Internal monitor was not properly initialized. Please report this to the "\
-                    "concurrent-ruby developers.")
-                end
-
+                monitor or raise("BUG: Internal monitor was not properly initialized. Please report this to the concurrent-ruby developers.")
                 monitor.synchronize { super }
               end
             RUBY
           end
         end
       end
+
+      def self.make_synchronized_on_truffleruby(klass)
+        klass.superclass.instance_methods(false).each do |method|
+          klass.class_eval <<-RUBY, __FILE__, __LINE__ + 1
+            def #{method}(*args, &block)    
+              # TODO (pitr-ch 01-Jul-2018): don't use internal TruffleRuby APIs  
+              Truffle::System.synchronized(self) { super(*args, &block) }
+            end
+          RUBY
+        end
+      end
     end
   end
 end
diff --git a/spec/concurrent/array_spec.rb b/spec/concurrent/array_spec.rb
index c0ecab38f..f79f8e077 100644
--- a/spec/concurrent/array_spec.rb
+++ b/spec/concurrent/array_spec.rb
@@ -68,7 +68,7 @@ module Concurrent
     context 'concurrency' do
       it do
         (1..Concurrent::ThreadSafe::Test::THREADS).map do |i|
-          in_thread do
+          in_thread(ary) do |ary|
             1000.times do
               ary << i
               ary.each { |x| x * 2 }
@@ -82,7 +82,7 @@ module Concurrent
     end
 
     describe '#slice' do
-      # This is mostly relevant on Rubinius and Truffle
+      # This is mostly relevant on Rubinius and TruffleRuby
       it 'correctly initializes the monitor' do
         ary.concat([0, 1, 2, 3, 4, 5, 6, 7, 8])