diff --git a/build-support/macros-and-definitions.cmake b/build-support/macros-and-definitions.cmake
index a37f9425b..ef7984484 100644
--- a/build-support/macros-and-definitions.cmake
+++ b/build-support/macros-and-definitions.cmake
@@ -921,20 +921,21 @@ macro(process_options)
     )
 
     file(
-      WRITE ${PROJECT_SOURCE_DIR}/doc/introspected-command-line.h
+      WRITE ${CMAKE_BINARY_DIR}/introspected-command-line-preamble.h
       "/* This file is automatically generated by
   CommandLine::PrintDoxygenUsage() from the CommandLine configuration
   in various example programs.  Do not edit this file!  Edit the
   CommandLine configuration in those files instead.
-  */
-  \n"
+  */\n"
     )
     add_custom_target(
       assemble-introspected-command-line
       # works on CMake 3.18 or newer > COMMAND ${CMAKE_COMMAND} -E cat
       # ${PROJECT_SOURCE_DIR}/testpy-output/*.command-line >
       # ${PROJECT_SOURCE_DIR}/doc/introspected-command-line.h
-      COMMAND ${cat_command} ${PROJECT_SOURCE_DIR}/testpy-output/*.command-line
+      COMMAND ${cat_command}
+              ${CMAKE_BINARY_DIR}/introspected-command-line-preamble.h
+              ${PROJECT_SOURCE_DIR}/testpy-output/*.command-line
               > ${PROJECT_SOURCE_DIR}/doc/introspected-command-line.h 2> NULL
       DEPENDS run-introspected-command-line
     )
diff --git a/ns3 b/ns3
index d917f5ba3..2a9040749 100755
--- a/ns3
+++ b/ns3
@@ -920,7 +920,8 @@ def build_step(args,
 
     # If we are building specific targets, we build them one by one
     if "build" in args:
-        non_executable_targets = ["check-version",
+        non_executable_targets = ["assemble-introspected-command-line",
+                                  "check-version",
                                   "cmake-format",
                                   "docs",
                                   "doxygen",
diff --git a/utils/tests/gitlab-ci-doc.yml b/utils/tests/gitlab-ci-doc.yml
index c7d5f7270..daf8cf4c4 100644
--- a/utils/tests/gitlab-ci-doc.yml
+++ b/utils/tests/gitlab-ci-doc.yml
@@ -7,7 +7,6 @@
     - pacman-key --init
     - pacman -Syu --noconfirm
       base-devel ninja cmake python ccache gsl gtk3 boost
-      git
       doxygen graphviz imagemagick dia texlive-core texlive-bin texlive-latexextra python-sphinx
     # no policy is a good policy.
     - mv /etc/ImageMagick-7/policy.xml /etc/ImageMagick-7/policy.xml.bak
@@ -27,6 +26,7 @@ doxygen:
     - export CCACHE_DIR=${PWD}/$CCACHE_BASEDIR_VALUE
     - CXX=$COMPILER ./ns3 configure --enable-examples --enable-tests --enable-asserts -d default
     - ./ns3 build
+    - ./ns3 build assemble-introspected-command-line
 #    - mkdir -p public/doxygen
 # The following four lines were needed when ns-3 had warnings, and
 # it was necessary to have a filter to check only the files tocuhed by a MR.
@@ -35,6 +35,9 @@ doxygen:
 #    - export CHANGED_FILES=$(git diff --name-only ns-3-origin/master --diff-filter=d | tr '\n' ' ' | sed 's/ $//g;s/ /\\\|/g')
 #    - doc/doxygen.warnings.report.sh -f "$CHANGED_FILES"
     - doc/doxygen.warnings.report.sh
+# Just need to check doc/introspected-command-line.h and doc/introspected-doxygen.h
+    - python3 utils/trim-trailing-whitespace.py --check doc/introspected-doxygen.h
+    - python3 utils/trim-trailing-whitespace.py --check doc/introspected-command-line.h
 #    - doxygen doc/doxygen.conf
 #    - mv doc/html/ public/doxygen
   cache: