diff --git a/lib/httpx/connection.rb b/lib/httpx/connection.rb
index 6b96c203..e5e69d94 100644
--- a/lib/httpx/connection.rb
+++ b/lib/httpx/connection.rb
@@ -540,7 +540,7 @@ module HTTPX
 
         if @total_timeout && @total_timeout.fires_in.negative?
           ex = TotalTimeoutError.new(@total_timeout.interval, "Timed out after #{@total_timeout.interval} seconds")
-          ex.set_backtrace(error.backtrace) if error.backtrace
+          ex.set_backtrace(error.backtrace)
           error = ex
         elsif connecting?
           error = error.to_connection_error
diff --git a/lib/httpx/options.rb b/lib/httpx/options.rb
index aea54f56..9cdc5469 100644
--- a/lib/httpx/options.rb
+++ b/lib/httpx/options.rb
@@ -111,7 +111,7 @@ module HTTPX
 
     def initialize(options = {})
       defaults = DEFAULT_OPTIONS.merge(options)
-      defaults.each do |(k, v)|
+      defaults.each do |k, v|
         next if v.nil?
 
         begin
@@ -185,6 +185,7 @@ module HTTPX
     end
 
     REQUEST_IVARS = %i[@params @form @json @body].freeze
+    private_constant :REQUEST_IVARS
 
     def ==(other)
       ivars = instance_variables | other.instance_variables
@@ -202,7 +203,7 @@ module HTTPX
     end
 
     def merge(other)
-      raise ArgumentError, "#{other.inspect} is not a valid set of options" unless other.respond_to?(:to_hash)
+      raise ArgumentError, "#{other} is not a valid set of options" unless other.respond_to?(:to_hash)
 
       h2 = other.to_hash
       return self if h2.empty?
diff --git a/lib/httpx/plugins/proxy.rb b/lib/httpx/plugins/proxy.rb
index b724b304..832a5795 100644
--- a/lib/httpx/plugins/proxy.rb
+++ b/lib/httpx/plugins/proxy.rb
@@ -5,7 +5,8 @@ require "ipaddr"
 require "forwardable"
 
 module HTTPX
-  HTTPProxyError = Class.new(Error)
+  class HTTPProxyError < Error; end
+
   module Plugins
     #
     # This plugin adds support for proxies. It ships with support for:
@@ -136,10 +137,11 @@ module HTTPX
         def __proxy_error?(response)
           error = response.error
           case error
-          when ResolveError
+          when NativeResolveError
             # failed resolving proxy domain
-            proxy_uri = error.connection.options.proxy.uri
-            proxy_uri.to_s == @_proxy_uris.first
+            error.connection.origin.to_s == @_proxy_uris.first
+          when ResolveError
+            error.message.end_with?(@_proxy_uris.first)
           when *PROXY_ERRORS
             # timeout errors connecting to proxy
             true
diff --git a/sig/connection.rbs b/sig/connection.rbs
index df3e2e30..34c4beb2 100644
--- a/sig/connection.rbs
+++ b/sig/connection.rbs
@@ -26,6 +26,7 @@ module HTTPX
     attr_reader state: Symbol
     attr_reader pending: Array[Request]
     attr_reader options: Options
+    attr_writer timers: untyped # Timers::Timer
 
     def addresses: () -> Array[ipaddr]?
 
@@ -37,7 +38,7 @@ module HTTPX
 
     def coalescable?: (Connection) -> bool
 
-    def create_idle: (?Hash[Symbol | String, untyped] options) -> Connection
+    def create_idle: (?Hash[Symbol, untyped] options) -> Connection
 
     def merge: (Connection) -> void
 
diff --git a/sig/options.rbs b/sig/options.rbs
index 86e396d7..87149618 100644
--- a/sig/options.rbs
+++ b/sig/options.rbs
@@ -45,7 +45,7 @@ module HTTPX
     attr_reader transport_options: Hash[untyped, untyped]?
 
     # addresses
-    attr_reader addresses: _ToAry[ipaddr]?
+    attr_reader addresses: Array[ipaddr]?
 
     # params
     attr_reader params: Transcoder::urlencoded_input?
@@ -103,7 +103,7 @@ module HTTPX
     attr_reader resolver_options: Hash[Symbol, untyped]?
 
     def ==: (untyped other) -> bool
-    def merge: (_ToHash[Symbol | String, untyped] other) -> instance
+    def merge: (_ToHash[Symbol, untyped] other) -> instance
     def to_hash: () -> Hash[Symbol, untyped]
 
     private
@@ -113,5 +113,5 @@ module HTTPX
     def initialize: (?options options) -> untyped
   end
 
-  type options = Options | Hash[Symbol | String, untyped]
+  type options = Options | Hash[Symbol, untyped]
 end