diff --git a/lib/httpx/connection.rb b/lib/httpx/connection.rb
index 39314db7..687f9d69 100644
--- a/lib/httpx/connection.rb
+++ b/lib/httpx/connection.rb
@@ -316,7 +316,7 @@ module HTTPX
           # * the number of inflight requests
           # * the number of pending requests
           # * whether the write buffer has bytes (i.e. for close handshake)
-          if @pending.size.zero? && @inflight.zero? && @write_buffer.empty?
+          if @pending.empty? && @inflight.zero? && @write_buffer.empty?
             log(level: 3) { "NO MORE REQUESTS..." }
             return
           end
@@ -360,7 +360,7 @@ module HTTPX
             break if @state == :closing || @state == :closed
 
             # exit #consume altogether if all outstanding requests have been dealt with
-            return if @pending.size.zero? && @inflight.zero?
+            return if @pending.empty? && @inflight.zero?
           end unless ((ints = interests).nil? || ints == :w || @state == :closing) && !epiped
 
           #
diff --git a/lib/httpx/connection/http2.rb b/lib/httpx/connection/http2.rb
index 185797e0..f812a5cc 100644
--- a/lib/httpx/connection/http2.rb
+++ b/lib/httpx/connection/http2.rb
@@ -365,7 +365,7 @@ module HTTPX
         ex.set_backtrace(caller)
         handle_error(ex)
       end
-      return unless is_connection_closed && @streams.size.zero?
+      return unless is_connection_closed && @streams.empty?
 
       emit(:close, is_connection_closed)
     end
diff --git a/lib/httpx/options.rb b/lib/httpx/options.rb
index 2bd97094..25b98fda 100644
--- a/lib/httpx/options.rb
+++ b/lib/httpx/options.rb
@@ -100,7 +100,7 @@ module HTTPX
       end
 
       def def_option(optname, *args, &block)
-        if args.size.zero? && !block
+        if args.empty? && !block
           class_eval(<<-OUT, __FILE__, __LINE__ + 1)
             def option_#{optname}(v); v; end # def option_smth(v); v; end
           OUT
diff --git a/lib/httpx/plugins/compression.rb b/lib/httpx/plugins/compression.rb
index aebf9f82..4e27655b 100644
--- a/lib/httpx/plugins/compression.rb
+++ b/lib/httpx/plugins/compression.rb
@@ -138,7 +138,7 @@ module HTTPX
         def each(&blk)
           return enum_for(__method__) unless blk
 
-          return deflate(&blk) if @buffer.size.zero?
+          return deflate(&blk) if @buffer.empty?
 
           @buffer.rewind
           @buffer.each(&blk)
@@ -152,7 +152,7 @@ module HTTPX
         private
 
         def deflate(&blk)
-          return unless @buffer.size.zero?
+          return unless @buffer.empty?
 
           @body.rewind
           @deflater.deflate(@body, @buffer, chunk_size: 16_384, &blk)
diff --git a/lib/httpx/plugins/compression/gzip.rb b/lib/httpx/plugins/compression/gzip.rb
index 56e06a37..e8913f7d 100644
--- a/lib/httpx/plugins/compression/gzip.rb
+++ b/lib/httpx/plugins/compression/gzip.rb
@@ -56,7 +56,7 @@ module HTTPX
 
         class Inflater
           def initialize(bytesize)
-            @inflater = Zlib::Inflate.new(32 + Zlib::MAX_WBITS)
+            @inflater = Zlib::Inflate.new(Zlib::MAX_WBITS + 32)
             @bytesize = bytesize
             @buffer = nil
           end
diff --git a/lib/httpx/plugins/grpc/message.rb b/lib/httpx/plugins/grpc/message.rb
index 83e095da..8ed96e8b 100644
--- a/lib/httpx/plugins/grpc/message.rb
+++ b/lib/httpx/plugins/grpc/message.rb
@@ -57,7 +57,7 @@ module HTTPX
 
             yield data
 
-            message = message.byteslice((5 + size)..-1)
+            message = message.byteslice((size + 5)..-1)
           end
         end
 
diff --git a/lib/httpx/plugins/retries.rb b/lib/httpx/plugins/retries.rb
index c01d306e..f413af23 100644
--- a/lib/httpx/plugins/retries.rb
+++ b/lib/httpx/plugins/retries.rb
@@ -26,7 +26,7 @@ module HTTPX
         ConnectionError,
         Connection::HTTP2::GoawayError,
       ].freeze
-      DEFAULT_JITTER = ->(interval) { interval * (0.5 * (1 + rand)) }
+      DEFAULT_JITTER = ->(interval) { interval * ((rand + 1) * 0.5) }
 
       if ENV.key?("HTTPX_NO_JITTER")
         def self.extra_options(options)