diff --git a/DESCRIPTION b/DESCRIPTION
index 92893d0..c35ef1a 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -1,7 +1,7 @@
 Package: litedown
 Type: Package
 Title: A Lightweight Version of R Markdown
-Version: 0.5.2
+Version: 0.5.3
 Authors@R: c(
     person("Yihui", "Xie", role = c("aut", "cre"), email = "xie@yihui.name", comment = c(ORCID = "0000-0003-0645-5666", URL = "https://yihui.org")),
     person("Tim", "Taylor", role = "ctb", comment = c(ORCID = "0000-0002-8587-7113")),
diff --git a/R/format.R b/R/format.R
index 135b996..8fec9a3 100644
--- a/R/format.R
+++ b/R/format.R
@@ -99,13 +99,18 @@ map_args = function(
   list(meta = meta, options = opts, ...)
 }
 
-# split YAML and body from text input, and normalize rmarkdown output formats in
-# YAML to litedown's formats
+# split YAML and body from text input
 yaml_body = function(text, ...) {
   res = xfun::yaml_body(text, use_yaml = FALSE, ...)
-  if (!length(out <- res$yaml[['output']])) {
+  if (!is.null(yaml <- normalize_yaml(res$yaml))) res$yaml = yaml
+  res
+}
+
+# normalize (rmarkdown) output formats in YAML to litedown's formats
+normalize_yaml = function(x) {
+  if (!length(out <- x[['output']])) {
     # if the key 'format' is provided, normalize it to 'output'
-    if (length(out <- res$yaml[['format']])) res$yaml$format = NULL else return(res)
+    if (length(out <- x[['format']])) x$format = NULL else return()
   }
   if (is.character(out)) out = set_names(vector('list', length(out)), out)
   if (!is.list(out))
@@ -117,8 +122,8 @@ yaml_body = function(text, ...) {
   }
   # normalize format names `(lite|mark)down::*_format` to `*`
   names(out) = gsub('^(lite|mark)down::+([^_]+)_.*', '\\2', names(out))
-  res$yaml$output = out
-  res
+  x$output = out
+  x
 }
 
 # get metadata from a certain field under an output format
diff --git a/R/site.R b/R/site.R
index 7f6c412..17b9525 100644
--- a/R/site.R
+++ b/R/site.R
@@ -261,7 +261,11 @@ fuse_book = function(input = '.', output = NULL, envir = parent.frame()) {
 
 # read the config file _litedown.yml
 yml_config = function(d) {
-  if (file_exists(cfg <- file.path(d, '_litedown.yml'))) xfun::taml_file(cfg)
+  if (file_exists(cfg <- file.path(d, '_litedown.yml'))) {
+    yaml = xfun::taml_file(cfg)
+    if (!is.null(yaml2 <- normalize_yaml(yaml))) yaml = yaml2
+    yaml
+  }
 }
 
 site_pattern = '[.][Rq]?md$'