diff --git a/lib/rdoc/rd/block_parser.ry b/lib/rdoc/rd/block_parser.ry
index 675d437208..a56a866593 100644
--- a/lib/rdoc/rd/block_parser.ry
+++ b/lib/rdoc/rd/block_parser.ry
@@ -230,8 +230,6 @@ end
 
 # :stopdoc:
 
-TMPFILE = ["rdtmp", $$, 0]
-
 MARK_TO_LEVEL = {
   '='    => 1,
   '=='   => 2,
@@ -341,15 +339,19 @@ def next_token # :nodoc:
     # non-RD part begin
     when /^=begin\s+(\w+)/
       part = $1
+=begin # not imported to RDoc
       if @in_part # if in non-RD part
         @part_content.push(line)
       else
         @in_part = part if @tree.filter[part] # if filter exists
 #  p "BEGIN_PART: #{@in_part}" # DEBUG
       end
+=end
+      @in_part = part
     # non-RD part end
-    when /^=end/
+    when /^=end(?:$|[\s\0\C-d\C-z])/
       if @in_part # if in non-RD part
+=begin # not imported to RDoc
 #  p "END_PART: #{@in_part}" # DEBUG
         # make Part-in object
         part = RDoc::RD::Part.new(@part_content.join(""), @tree, "r")
@@ -360,20 +362,22 @@ def next_token # :nodoc:
         if @tree.filter[@in_part].mode == :rd # if output is RD formatted
           subtree = parse_subtree(part_out.to_a)
         else # if output is target formatted
-          basename = TMPFILE.join('.')
-          TMPFILE[-1] += 1
-          tmpfile = open(@tree.tmp_dir + "/" + basename + ".#{@in_part}", "w")
-          tmpfile.print(part_out)
-          tmpfile.close
+          basename = Tempfile.create(["rdtmp", ".#{@in_part}"], @tree.tmp_dir) do |tmpfile|
+            tmpfile.print(part_out)
+            File.basename(tmpfile.path)
+          end
           subtree = parse_subtree(["=begin\n", "<<< #{basename}\n", "=end\n"])
         end
         @in_part = nil
         return [:SUBTREE, subtree]
+=end
       end
     else
+=begin # not imported to RDoc
       if @in_part # if in non-RD part
         @part_content.push(line)
       end
+=end
     end
   end
 
diff --git a/test/rdoc/test_rdoc_rd_block_parser.rb b/test/rdoc/test_rdoc_rd_block_parser.rb
index 22f432eaf4..ca0ac9f9e9 100644
--- a/test/rdoc/test_rdoc_rd_block_parser.rb
+++ b/test/rdoc/test_rdoc_rd_block_parser.rb
@@ -168,6 +168,27 @@ def test_parse_include_subtree
     tf.close!
   end
 
+=begin
+  def test_parse_include_other_format
+    @block_parser.include_path = [Dir.tmpdir]
+
+    expected =
+      doc(
+        blank_line,
+        para("include ((*worked*))"),
+        blank_line,
+        blank_line)
+
+    str = <<~STR
+    =begin nonrd
+    <<< worked
+    =end
+    STR
+
+    assert_equal(expected, @block_parser.parse str.lines.to_a)
+  end
+=end
+
   def test_parse_heading
     assert_equal doc(head(1, "H")), parse("= H")
     assert_equal doc(head(2, "H")), parse("== H")