diff --git a/lib/capybara/server.rb b/lib/capybara/server.rb
index 24f0314a..0a005779 100644
--- a/lib/capybara/server.rb
+++ b/lib/capybara/server.rb
@@ -61,7 +61,7 @@ module Capybara
     def wait_for_pending_requests
       timer = Capybara::Helpers.timer(expire_in: 60)
       while pending_requests?
-        raise 'Requests did not finish in 60 seconds' if timer.expired?
+        raise "Requests did not finish in 60 seconds: #{middleware.pending_requests}" if timer.expired?
 
         sleep 0.01
       end
diff --git a/lib/capybara/server/middleware.rb b/lib/capybara/server/middleware.rb
index 5305a1e2..01cedb6f 100644
--- a/lib/capybara/server/middleware.rb
+++ b/lib/capybara/server/middleware.rb
@@ -4,19 +4,25 @@ module Capybara
   class Server
     class Middleware
       class Counter
-        attr_reader :value
-
         def initialize
-          @value = 0
+          @value = []
           @mutex = Mutex.new
         end
 
-        def increment
-          @mutex.synchronize { @value += 1 }
+        def increment(uri)
+          @mutex.synchronize { @value.push(uri) }
         end
 
-        def decrement
-          @mutex.synchronize { @value -= 1 }
+        def decrement(uri)
+          @mutex.synchronize { @value.delete_at(@value.index(uri) || @value.length) }
+        end
+
+        def positive?
+          @mutex.synchronize { @value.length.positive? }
+        end
+
+        def value
+          @mutex.synchronize { @value }
         end
       end
 
@@ -31,8 +37,12 @@ module Capybara
         @server_errors = server_errors
       end
 
+      def pending_requests
+        @counter.value
+      end
+
       def pending_requests?
-        @counter.value.positive?
+        @counter.positive?
       end
 
       def clear_error
@@ -43,14 +53,14 @@ module Capybara
         if env['PATH_INFO'] == '/__identify__'
           [200, {}, [@app.object_id.to_s]]
         else
-          @counter.increment
+          @counter.increment(env['REQUEST_URI'])
           begin
             @extended_app.call(env)
           rescue *@server_errors => e
             @error ||= e
             raise e
           ensure
-            @counter.decrement
+            @counter.decrement(env['REQUEST_URI'])
           end
         end
       end
diff --git a/spec/server_spec.rb b/spec/server_spec.rb
index 03098f79..b85503fc 100644
--- a/spec/server_spec.rb
+++ b/spec/server_spec.rb
@@ -239,6 +239,26 @@ RSpec.describe Capybara::Server do
     end
   end
 
+  it 'should raise an error when there are pending requests' do
+    app = proc do |env|
+      request = Rack::Request.new(env)
+      sleep request.params['wait_time'].to_f
+      [200, {}, ['Hello Server!']]
+    end
+
+    server = described_class.new(app).boot
+
+    expect do
+      start_request(server, 59.0)
+      server.wait_for_pending_requests
+    end.not_to raise_error
+
+    expect do
+      start_request(server, 61.0)
+      server.wait_for_pending_requests
+    end.to raise_error('Requests did not finish in 60 seconds: ["/?wait_time=61.0"]')
+  end
+
   it 'is not #responsive? when Net::HTTP raises a SystemCallError' do
     app = -> { [200, {}, ['Hello, world']] }
     server = described_class.new(app)