diff --git a/lib/webrick/httpresponse.rb b/lib/webrick/httpresponse.rb
index 820579237f..6d77692140 100644
--- a/lib/webrick/httpresponse.rb
+++ b/lib/webrick/httpresponse.rb
@@ -433,7 +433,12 @@ module WEBrick
             size = @header['content-length']
             size = size.to_i if size
           end
-          @sent_size = IO.copy_stream(@body, socket, size, offset)
+          begin
+            @sent_size = IO.copy_stream(@body, socket, size, offset)
+          rescue NotImplementedError
+            @body.seek(offset, IO::SEEK_SET)
+            @sent_size = IO.copy_stream(@body, socket, size)
+          end
         end
       ensure
         @body.close
diff --git a/lib/webrick/httpservlet/filehandler.rb b/lib/webrick/httpservlet/filehandler.rb
index e4d892ee66..0072e81ac6 100644
--- a/lib/webrick/httpservlet/filehandler.rb
+++ b/lib/webrick/httpservlet/filehandler.rb
@@ -100,7 +100,12 @@ module WEBrick
                 "#{CRLF}"
               )
 
-              IO.copy_stream(body, socket, last - first + 1, first)
+              begin
+                IO.copy_stream(body, socket, last - first + 1, first)
+              rescue NotImplementedError
+                body.seek(first, IO::SEEK_SET)
+                IO.copy_stream(body, socket, last - first + 1)
+              end
               socket.write(CRLF)
             end while parts[0]
             socket.write("--#{boundary}--#{CRLF}")