diff --git a/lib/rdoc/parser/ripper_state_lex.rb b/lib/rdoc/parser/ripper_state_lex.rb
index 773a830450..3c761f985d 100644
--- a/lib/rdoc/parser/ripper_state_lex.rb
+++ b/lib/rdoc/parser/ripper_state_lex.rb
@@ -555,6 +555,10 @@ def get_squashed_tk
         tk[:text] += tk_ahead[:text]
         tk[:kind] = tk_ahead[:kind]
         tk[:state] = tk_ahead[:state]
+      when :on_heredoc_beg, :on_tstring, :on_dstring # frozen/non-frozen string literal
+        tk[:text] += tk_ahead[:text]
+        tk[:kind] = tk_ahead[:kind]
+        tk[:state] = tk_ahead[:state]
       else
         @buf.unshift tk_ahead
       end
diff --git a/test/test_rdoc_parser_ruby.rb b/test/test_rdoc_parser_ruby.rb
index 8e31141f59..6f7413a0b4 100644
--- a/test/test_rdoc_parser_ruby.rb
+++ b/test/test_rdoc_parser_ruby.rb
@@ -2848,6 +2848,35 @@ def blah()
     assert_equal expected, markup_code
   end
 
+  def test_parse_mutable_heredocbeg
+    @filename = 'file.rb'
+    util_parser <<RUBY
+class Foo
+  def blah()
+    @str = -<<-EOM
+    EOM
+  end
+end
+RUBY
+
+    expected = <<EXPECTED
+  <span class="ruby-keyword">def</span> <span class="ruby-identifier ruby-title">blah</span>()
+    <span class="ruby-ivar">@str</span> = <span class="ruby-identifier">-&lt;&lt;-EOM</span>
+<span class="ruby-value"></span><span class="ruby-identifier">    EOM</span>
+  <span class="ruby-keyword">end</span>
+EXPECTED
+    expected = expected.rstrip
+
+    @parser.scan
+
+    foo = @top_level.classes.first
+    assert_equal 'Foo', foo.full_name
+
+    blah = foo.method_list.first
+    markup_code = blah.markup_code.sub(/^.*\n/, '')
+    assert_equal expected, markup_code
+  end
+
   def test_parse_statements_method_oneliner_with_regexp
     util_parser <<RUBY
 class Foo