diff --git a/nixos/doc/manual/default.nix b/nixos/doc/manual/default.nix
index 7e0d4ad92b01..9413d71a34cf 100644
--- a/nixos/doc/manual/default.nix
+++ b/nixos/doc/manual/default.nix
@@ -94,25 +94,43 @@ let
     "--stringparam chunk.toc ${toc}"
   ];
 
+  manual-combined = runCommand "nixos-manual-combined"
+    { inherit sources;
+      buildInputs = [ libxml2 libxslt ];
+      meta.description = "The NixOS manual as plain docbook XML";
+    }
+    ''
+      ${copySources}
+
+      xmllint --xinclude --output ./manual-combined.xml ./manual.xml
+      xmllint --xinclude --noxincludenode \
+         --output ./man-pages-combined.xml ./man-pages.xml
+
+      xmllint --debug --noout --nonet \
+        --relaxng ${docbook5}/xml/rng/docbook/docbook.rng \
+        manual-combined.xml
+      xmllint --debug --noout --nonet \
+        --relaxng ${docbook5}/xml/rng/docbook/docbook.rng \
+        man-pages-combined.xml
+
+
+      mkdir $out
+      cp manual-combined.xml $out/
+      cp man-pages-combined.xml $out/
+    '';
+
   olinkDB = runCommand "manual-olinkdb"
     { inherit sources;
       buildInputs = [ libxml2 libxslt ];
     }
     ''
-      ${copySources}
-
       xsltproc \
         ${manualXsltprocOptions} \
         --stringparam collect.xref.targets only \
         --stringparam targets.filename "$out/manual.db" \
-        --nonet --xinclude \
+        --nonet \
         ${docbook5_xsl}/xml/xsl/docbook/xhtml/chunktoc.xsl \
-        ./manual.xml
-
-      # Check the validity of the man pages sources.
-      xmllint --noout --nonet --xinclude --noxincludenode \
-        --relaxng ${docbook5}/xml/rng/docbook/docbook.rng \
-        ./man-pages.xml
+        ${manual-combined}/manual-combined.xml
 
       cat > "$out/olinkdb.xml" <<EOF
       <?xml version="1.0" encoding="utf-8"?>
@@ -158,21 +176,15 @@ in rec {
       allowedReferences = ["out"];
     }
     ''
-      ${copySources}
-
-      # Check the validity of the manual sources.
-      xmllint --noout --nonet --xinclude --noxincludenode \
-        --relaxng ${docbook5}/xml/rng/docbook/docbook.rng \
-        manual.xml
-
       # Generate the HTML manual.
       dst=$out/share/doc/nixos
       mkdir -p $dst
       xsltproc \
         ${manualXsltprocOptions} \
         --stringparam target.database.document "${olinkDB}/olinkdb.xml" \
-        --nonet --xinclude --output $dst/ \
-        ${docbook5_xsl}/xml/xsl/docbook/xhtml/chunktoc.xsl ./manual.xml
+        --nonet --output $dst/ \
+        ${docbook5_xsl}/xml/xsl/docbook/xhtml/chunktoc.xsl \
+        ${manual-combined}/manual-combined.xml
 
       mkdir -p $dst/images/callouts
       cp ${docbook5_xsl}/xml/xsl/docbook/images/callouts/*.gif $dst/images/callouts/
@@ -190,13 +202,6 @@ in rec {
       buildInputs = [ libxml2 libxslt zip ];
     }
     ''
-      ${copySources}
-
-      # Check the validity of the manual sources.
-      xmllint --noout --nonet --xinclude --noxincludenode \
-        --relaxng ${docbook5}/xml/rng/docbook/docbook.rng \
-        manual.xml
-
       # Generate the epub manual.
       dst=$out/share/doc/nixos
 
@@ -204,10 +209,11 @@ in rec {
         ${manualXsltprocOptions} \
         --stringparam target.database.document "${olinkDB}/olinkdb.xml" \
         --nonet --xinclude --output $dst/epub/ \
-        ${docbook5_xsl}/xml/xsl/docbook/epub/docbook.xsl ./manual.xml
+        ${docbook5_xsl}/xml/xsl/docbook/epub/docbook.xsl \
+        ${manual-combined}/manual-combined.xml
 
       mkdir -p $dst/epub/OEBPS/images/callouts
-      cp -r ${docbook5_xsl}/xml/xsl/docbook/images/callouts/*.gif $dst/epub/OEBPS/images/callouts
+      cp -r ${docbook5_xsl}/xml/xsl/docbook/images/callouts/*.gif $dst/epub/OEBPS/images/callouts # */
       echo "application/epub+zip" > mimetype
       manual="$dst/nixos-manual.epub"
       zip -0Xq "$manual" mimetype
@@ -227,23 +233,16 @@ in rec {
       allowedReferences = ["out"];
     }
     ''
-      ${copySources}
-
-      # Check the validity of the man pages sources.
-      xmllint --noout --nonet --xinclude --noxincludenode \
-        --relaxng ${docbook5}/xml/rng/docbook/docbook.rng \
-        ./man-pages.xml
-
       # Generate manpages.
       mkdir -p $out/share/man
-      xsltproc --nonet --xinclude \
+      xsltproc --nonet \
         --param man.output.in.separate.dir 1 \
         --param man.output.base.dir "'$out/share/man/'" \
         --param man.endnotes.are.numbered 0 \
         --param man.break.after.slash 1 \
         --stringparam target.database.document "${olinkDB}/olinkdb.xml" \
         ${docbook5_xsl}/xml/xsl/docbook/manpages/docbook.xsl \
-        ./man-pages.xml
+        ${manual-combined}/man-pages-combined.xml
     '';
 
 }