diff --git a/lib/net/http/persistent/pool.rb b/lib/net/http/persistent/pool.rb
index 220c70e..db63822 100644
--- a/lib/net/http/persistent/pool.rb
+++ b/lib/net/http/persistent/pool.rb
@@ -4,7 +4,7 @@ class Net::HTTP::Persistent::Pool < ConnectionPool # :nodoc:
   attr_reader :key # :nodoc:
 
   def initialize(options = {}, &block)
-    super
+    super(**options, &block)
 
     @available = Net::HTTP::Persistent::TimedStackMulti.new(@size, &block)
     @key = "current-#{@available.object_id}"
diff --git a/lib/net/http/persistent/timed_stack_multi.rb b/lib/net/http/persistent/timed_stack_multi.rb
index 9924a0a..ac7fdf8 100644
--- a/lib/net/http/persistent/timed_stack_multi.rb
+++ b/lib/net/http/persistent/timed_stack_multi.rb
@@ -1,5 +1,10 @@
 class Net::HTTP::Persistent::TimedStackMulti < ConnectionPool::TimedStack # :nodoc:
 
+  ##
+  # Detects if ConnectionPool 3.0+ is being used (needed for TimedStack subclass compatibility)
+
+  CP_USES_KEYWORD_ARGS = Gem::Version.new(ConnectionPool::VERSION) >= Gem::Version.new('3.0.0') # :nodoc:
+
   ##
   # Returns a new hash that has arrays for keys
   #
@@ -11,7 +16,11 @@ def self.hash_of_arrays # :nodoc:
   end
 
   def initialize(size = 0, &block)
-    super
+    if CP_USES_KEYWORD_ARGS
+      super(size: size, &block)
+    else
+      super(size, &block)
+    end
 
     @enqueued = 0
     @ques = self.class.hash_of_arrays
diff --git a/net-http-persistent.gemspec b/net-http-persistent.gemspec
index 58ac1db..1c6b794 100644
--- a/net-http-persistent.gemspec
+++ b/net-http-persistent.gemspec
@@ -17,7 +17,7 @@ Gem::Specification.new do |s|
   s.required_ruby_version = ">= 2.4".freeze
   s.summary = "Manages persistent connections using Net::HTTP including a thread pool for connecting to multiple hosts".freeze
 
-  s.add_runtime_dependency(%q<connection_pool>.freeze, ["~> 2.2", ">= 2.2.4"])
+  s.add_runtime_dependency(%q<connection_pool>.freeze, [">= 2.2.4", "< 4"])
   s.add_runtime_dependency(%q<cgi>.freeze, "~> 0.5.1")
 end
 
diff --git a/test/test_net_http_persistent_timed_stack_multi.rb b/test/test_net_http_persistent_timed_stack_multi.rb
index 38e191c..9288f92 100644
--- a/test/test_net_http_persistent_timed_stack_multi.rb
+++ b/test/test_net_http_persistent_timed_stack_multi.rb
@@ -29,7 +29,7 @@ def test_empty_eh
 
     assert_empty stack
 
-    stack.push connection_args: popped
+    stack.push popped, connection_args: 'default'
 
     refute_empty stack
   end
@@ -43,7 +43,7 @@ def test_length
 
     assert_equal 0, stack.length
 
-    stack.push connection_args: popped
+    stack.push popped, connection_args: 'default'
 
     assert_equal 1, stack.length
   end
@@ -113,7 +113,7 @@ def test_push
 
     conn = stack.pop
 
-    stack.push connection_args: conn
+    stack.push conn, connection_args: 'default'
 
     refute_empty stack
   end
@@ -125,14 +125,16 @@ def test_push_shutdown
       called << object
     end
 
-    @stack.push connection_args: Object.new
+    obj = Object.new
+    @stack.push obj, connection_args: 'default'
 
     refute_empty called
     assert_empty @stack
   end
 
   def test_shutdown
-    @stack.push connection_args: Object.new
+    obj = Object.new
+    @stack.push obj, connection_args: 'default'
 
     called = []