diff --git a/parse.y b/parse.y
index 1935160fb2..cf05a9c891 100644
--- a/parse.y
+++ b/parse.y
@@ -6406,6 +6406,7 @@ parser_heredoc_identifier(struct parser_params *parser)
     int c = nextc(), term, func = 0;
     int token = tSTRING_BEG;
     long len;
+    int newline = 0;
 
     if (c == '-') {
 	c = nextc();
@@ -6432,11 +6433,15 @@ parser_heredoc_identifier(struct parser_params *parser)
 	term = c;
 	while ((c = nextc()) != -1 && c != term) {
 	    if (tokadd_mbchar(c) == -1) return 0;
+	    if (c == '\n') newline = 1;
 	}
 	if (c == -1) {
 	    compile_error(PARSER_ARG "unterminated here document identifier");
 	    return 0;
 	}
+	if (newline) {
+	    rb_warn0("here document identifier contains newline");
+	}
 	break;
 
       default:
diff --git a/test/ruby/test_syntax.rb b/test/ruby/test_syntax.rb
index ad1f0d8981..4c4e840e5e 100644
--- a/test/ruby/test_syntax.rb
+++ b/test/ruby/test_syntax.rb
@@ -745,6 +745,12 @@ eom
     assert_syntax_error("puts <<""EOS\n""ng\n""EOS\r""NO\n", /can't find string "EOS" anywhere before EOF/)
   end
 
+  def test_heredoc_newline
+    assert_warn(/contains newline/) do
+      eval("<<\"EOS\n\"\nEOS\n")
+    end
+  end
+
   def test__END___cr
     assert_syntax_error("__END__\r<<<<<\n", /unexpected <</)
   end