diff --git a/doc/Makefile b/doc/Makefile
index f3a4d6b5aafd..52d1f4630a8e 100644
--- a/doc/Makefile
+++ b/doc/Makefile
@@ -3,6 +3,9 @@ MD_TARGETS=$(addsuffix .xml, $(basename $(wildcard ./*.md ./**/*.md)))
 .PHONY: all
 all: validate out/html/index.html out/epub/manual.epub
 
+.PHONY: debug
+debug:
+	nix-shell --run "xmloscopy --docbook5 ./manual.xml ./manual-full.xml"
 .PHONY: clean
 clean:
 	rm -f ${MD_TARGETS} .version manual-full.xml
diff --git a/doc/contributing.xml b/doc/contributing.xml
index 8eed9c5416e8..7aa0df271ff4 100644
--- a/doc/contributing.xml
+++ b/doc/contributing.xml
@@ -16,9 +16,8 @@ subdirectory of the Nixpkgs repository.</para>
   [nix-shell]$ make
 </screen>
 
-<para>If you experience problems, run <command>xmloscopy --docbook5
-./manual.xml ./manual-full.xml</command> inside the nix-shell to help
-understand the docbook errors.</para>
+<para>If you experience problems, run <command>make debug</command>
+to help understand the docbook errors.</para>
 
 <para>After making modifications to the manual, it's important to
 build it before committing. You can do that as follows: