diff --git a/NEWS.md b/NEWS.md
index 4ba49c77..86553566 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,6 +1,9 @@
 # xml2 (development version)
 
+* `xml_serialize()` now includes the document type so that `xml_unserialize()` works also for HTML documents (#407, @HenrikBengtsson).
+
 * Remove unused dependencies on glue, withr and lifecycle (@mgirlich).
+
 * `print()` is faster for very long `xml_nodeset` inputs (#366, @michaelchirico).
 
 # xml2 1.3.5
diff --git a/R/xml_serialize.R b/R/xml_serialize.R
index 1869268e..d2cdcb9b 100644
--- a/R/xml_serialize.R
+++ b/R/xml_serialize.R
@@ -22,7 +22,7 @@ xml_serialize.xml_document <- function(object, connection, ...) {
     connection <- file(connection, "w", raw = TRUE)
     on.exit(close(connection))
   }
-  serialize(structure(as.character(object, ...), class = "xml_serialized_document"), connection)
+  serialize(structure(as.character(object, ...), doc_type = doc_type(object), class = "xml_serialized_document"), connection)
 }
 
 #' @export
@@ -64,7 +64,13 @@ xml_unserialize <- function(connection, ...) {
     # Select only the root
     res <- xml_find_first(x, "/node()")
   } else if (inherits(object, "xml_serialized_document")) {
-    res <- read_xml(unclass(object), ...)
+    read_xml_int <- function(object, as_html = FALSE, ...) {
+      if (missing(as_html)) {
+        as_html <- identical(attr(object, "doc_type", exact = TRUE), "html")
+      }
+      read_xml(unclass(object), as_html = as_html, ...)
+    }
+    res <- read_xml_int(unclass(object), ...)
   } else {
     abort("Not a serialized xml2 object")
   }
diff --git a/tests/testthat/test-xml_serialize.R b/tests/testthat/test-xml_serialize.R
index 395dfb0c..825ead6a 100644
--- a/tests/testthat/test-xml_serialize.R
+++ b/tests/testthat/test-xml_serialize.R
@@ -2,6 +2,7 @@ x <- read_xml("<a>
   <b><c>123</c></b>
   <b><c>456</c></b>
   </a>")
+  
 test_that("xml_serialize and xml_unserialize work with xml_document input", {
   out <- xml_unserialize(xml_serialize(x, NULL))
   expect_identical(as.character(x), as.character(out))
@@ -37,6 +38,20 @@ test_that("xml_serialize and xml_unserialize work with xml_nodeset input", {
   expect_identical(as.character(xml_unserialize(f)), as.character(b))
 })
 
+test_that("xml_serialize and xml_unserialize work with HTML-based xml_document input", {
+  file <- system.file("extdata", "r-project.html", package = "xml2")
+  x <- read_html(file)
+
+  out <- xml_unserialize(xml_serialize(x, NULL))
+  expect_identical(as.character(x), as.character(out))
+
+  f <- tempfile()
+  on.exit(unlink(f))
+
+  xml_serialize(x, f)
+  expect_identical(as.character(xml_unserialize(f)), as.character(x))
+})
+
 test_that("xml_unserialize throws an error if given a invalid object", {
   expect_error(xml_unserialize(serialize(1, NULL)), "Not a serialized xml2 object")
 })