diff --git a/lib/rdoc/generator/json_index.rb b/lib/rdoc/generator/json_index.rb
index 931438b3c3..ea9384e6d3 100644
--- a/lib/rdoc/generator/json_index.rb
+++ b/lib/rdoc/generator/json_index.rb
@@ -170,7 +170,7 @@ def generate_gzipped
     outfile           = out_dir + "#{search_index_file}.gz"
 
     debug_msg "Reading the JSON index file from %s" % search_index_file
-    search_index = search_index_file.read
+    search_index = search_index_file.read(mode: 'r:utf-8')
 
     debug_msg "Writing gzipped search index to %s" % outfile
 
diff --git a/lib/rdoc/parser.rb b/lib/rdoc/parser.rb
index 5abc374bf7..89ac3f1c2a 100644
--- a/lib/rdoc/parser.rb
+++ b/lib/rdoc/parser.rb
@@ -78,7 +78,7 @@ def self.binary?(file)
 
     return true if s[0, 2] == Marshal.dump('')[0, 2] or s.index("\x00")
 
-    mode = "r"
+    mode = 'r:utf-8' # default source encoding has been chagened to utf-8
     s.sub!(/\A#!.*\n/, '')     # assume shebang line isn't longer than 1024.
     encoding = s[/^\s*\#\s*(?:-\*-\s*)?(?:en)?coding:\s*([^\s;]+?)(?:-\*-|[\s;])/, 1]
     mode = "rb:#{encoding}" if encoding
@@ -180,7 +180,9 @@ def self.check_modeline file_name
     return nil if /coding:/i =~ type
 
     type.downcase
-  rescue ArgumentError # invalid byte sequence, etc.
+  rescue ArgumentError
+  rescue Encoding::InvalidByteSequenceError # invalid byte sequence
+  
   end
 
   ##