diff --git a/.github/workflows/cygwin.yml b/.github/workflows/cygwin.yml
index 87e767f..fa4e2a0 100644
--- a/.github/workflows/cygwin.yml
+++ b/.github/workflows/cygwin.yml
@@ -10,7 +10,7 @@ jobs:
     - uses: actions/checkout@v6.0.2
     - uses: cygwin/cygwin-install-action@v6.1
       with:
-        packages: gcc-core make binutils libssl-devel xmlto asciidoc
+        packages: gcc-core make binutils libssl-devel xmlto asciidoc docbook-xml45
     - name: Build
       shell: bash {0}
       run: make && make docs
diff --git a/INSTALL.md b/INSTALL.md
index d61f59c..b91643d 100644
--- a/INSTALL.md
+++ b/INSTALL.md
@@ -98,7 +98,7 @@ Install Cygwin from [cygwin web site](https://cygwin.com).
 
 Following packages are required :
 ```
-$ setup-x86_64.exe -n -q -P gcc-core,make,binutils,libssl-devel,xmlto,asciidoc
+$ setup-x86_64.exe -n -q -P gcc-core,make,binutils,libssl-devel,xmlto,asciidoc,docbook-xml45
 ```
 
 To build :
diff --git a/docs/Makefile b/docs/Makefile
index 5bcd755..8e71490 100644
--- a/docs/Makefile
+++ b/docs/Makefile
@@ -21,7 +21,7 @@ clean:
 	asciidoc -d manpage -arevnumber=$(version) -arevdate=$(version_date) $<
 
 %.1: %.1.xml
-	xmlto --skip-validation man $<
+	xmlto man $<
 
 %.html: %.adoc
 	asciidoc $<