diff --git a/lib/webrick/server.rb b/lib/webrick/server.rb
index 5e83b692db..52a09f5186 100644
--- a/lib/webrick/server.rb
+++ b/lib/webrick/server.rb
@@ -251,17 +251,26 @@ module WEBrick
     # the client socket.
 
     def accept_client(svr)
-      sock = nil
-      begin
-        sock = svr.accept
-        Utils::set_non_blocking(sock)
-      rescue Errno::ECONNRESET, Errno::ECONNABORTED,
-             Errno::EPROTO, Errno::EINVAL
-      rescue StandardError => ex
-        msg = "#{ex.class}: #{ex.message}\n\t#{ex.backtrace[0]}"
-        @logger.error msg
+      case sock = svr.to_io.accept_nonblock(exception: false)
+      when :wait_readable
+        nil
+      else
+        if svr.respond_to?(:start_immediately)
+          sock = OpenSSL::SSL::SSLSocket.new(sock, ssl_context)
+          sock.sync_close = true
+          # we cannot do OpenSSL::SSL::SSLSocket#accept here because
+          # a slow client can prevent us from accepting connections
+          # from other clients
+        end
+        sock
       end
-      return sock
+    rescue Errno::ECONNRESET, Errno::ECONNABORTED,
+           Errno::EPROTO, Errno::EINVAL
+      nil
+    rescue StandardError => ex
+      msg = "#{ex.class}: #{ex.message}\n\t#{ex.backtrace[0]}"
+      @logger.error msg
+      nil
     end
 
     ##
@@ -284,6 +293,11 @@ module WEBrick
             @logger.debug "accept: <address unknown>"
             raise
           end
+          if sock.respond_to?(:sync_close=) && @config[:SSLStartImmediately]
+            WEBrick::Utils.timeout(@config[:RequestTimeout]) do
+              sock.accept # OpenSSL::SSL::SSLSocket#accept
+            end
+          end
           call_callback(:AcceptCallback, sock)
           block ? block.call(sock) : run(sock)
         rescue Errno::ENOTCONN
diff --git a/test/webrick/test_ssl_server.rb b/test/webrick/test_ssl_server.rb
index f6d5250365..64cf25f78b 100644
--- a/test/webrick/test_ssl_server.rb
+++ b/test/webrick/test_ssl_server.rb
@@ -2,6 +2,7 @@ require "test/unit"
 require "webrick"
 require "webrick/ssl"
 require_relative "utils"
+require 'timeout'
 
 class TestWEBrickSSLServer < Test::Unit::TestCase
   class Echo < WEBrick::GenericServer
@@ -37,4 +38,30 @@ class TestWEBrickSSLServer < Test::Unit::TestCase
       io.close
     }
   end
+
+  def test_slow_connect
+    poke = lambda do |io, msg|
+      begin
+        sock = OpenSSL::SSL::SSLSocket.new(io)
+        sock.connect
+        sock.puts(msg)
+        assert_equal "#{msg}\n", sock.gets, msg
+      ensure
+        sock&.close
+        io.close
+      end
+    end
+    config = {
+      :SSLEnable => true,
+      :SSLCertName => "/C=JP/O=www.ruby-lang.org/CN=Ruby",
+    }
+    Timeout.timeout(10) do
+      TestWEBrick.start_server(Echo, config) do |server, addr, port, log|
+        outer = TCPSocket.new(addr, port)
+        inner = TCPSocket.new(addr, port)
+        poke.call(inner, 'fast TLS negotiation')
+        poke.call(outer, 'slow TLS negotiation')
+      end
+    end
+  end
 end