diff --git a/DESCRIPTION b/DESCRIPTION
index d214d8c684..ea9d965b74 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -1,7 +1,7 @@
 Type: Package
 Package: rmarkdown
 Title: Dynamic Documents for R
-Version: 2.25.2
+Version: 2.25.3
 Authors@R: c(
     person("JJ", "Allaire", , "jj@posit.co", role = "aut"),
     person("Yihui", "Xie", , "xie@yihui.name", role = c("aut", "cre"), comment = c(ORCID = "0000-0003-0645-5666")),
diff --git a/R/html_document_base.R b/R/html_document_base.R
index 8fccb41d4a..d2dff82b1c 100644
--- a/R/html_document_base.R
+++ b/R/html_document_base.R
@@ -251,6 +251,11 @@ html_document_base <- function(theme = NULL,
 }
 
 extract_preserve_chunks <- function(input_file, extract = extractPreserveChunks) {
+  # Don't try to modify the input file if it's not .md, otherwise the original
+  # input could be corrupted (#2534). In theory, preserved chunks should only
+  # exist in the intermediate .md file from knit(). If the .md file is not
+  # intermediate but original, this processing should be harmless.
+  if (!xfun::file_ext(input_file) %in% c('md', 'markdown')) return()
   input_str <- one_string(read_utf8(input_file))
   preserve <- extract(input_str)
   if (!identical(preserve$value, input_str)) write_utf8(preserve$value, input_file)