diff --git a/lib/restclient/utils.rb b/lib/restclient/utils.rb
index 99078f8..bbcf1d3 100644
--- a/lib/restclient/utils.rb
+++ b/lib/restclient/utils.rb
@@ -4,25 +4,28 @@ module RestClient
 
     # Return encoding from an HTTP header hash.
     #
+    # We use the RFC 7231 specification and do not impose a default encoding on
+    # text. This differs from the older RFC 2616 behavior, which specifies
+    # using ISO-8859-1 for text/* content types without a charset.
+    #
+    # Strings will effectively end up using `Encoding.default_external` when
+    # this method returns nil.
+    #
     # @param headers [Hash]
     #
-    # @return [String] encoding
+    # @return [String, nil] encoding Return the string encoding or nil if no
+    #   header is found.
     #
     def self.get_encoding_from_headers(headers)
       type_header = headers[:content_type]
       return nil unless type_header
 
-      content_type, params = cgi_parse_header(type_header)
+      _content_type, params = cgi_parse_header(type_header)
 
       if params.include?('charset')
         return params.fetch('charset').gsub(/(\A["']*)|(["']*\z)/, '')
       end
 
-      # HTTP typically defaults to ISO-8859-1 when not specified.
-      if content_type.include?('text')
-        return 'ISO-8859-1'
-      end
-
       nil
     end
 
@@ -69,7 +72,7 @@ module RestClient
       pdict = {}
 
       begin
-        while p = parts.next
+        while (p = parts.next)
           i = p.index('=')
           if i
             name = p[0...i].strip.downcase
diff --git a/spec/unit/utils_spec.rb b/spec/unit/utils_spec.rb
index 05e7430..f29ab57 100644
--- a/spec/unit/utils_spec.rb
+++ b/spec/unit/utils_spec.rb
@@ -2,10 +2,10 @@ require 'spec_helper'
 
 describe RestClient::Utils do
   describe '.get_encoding_from_headers' do
-    it 'assumes ISO-8859-1 by default for text' do
+    it 'assumes no encoding by default for text' do
       headers = {:content_type => 'text/plain'}
       RestClient::Utils.get_encoding_from_headers(headers).
-        should eq 'ISO-8859-1'
+        should eq nil
     end
 
     it 'returns nil on failures' do