diff --git a/qt6-after/qt6-migrated-legatus/new_docker_build_release2.sh b/qt6-after/qt6-migrated-legatus/new_docker_build_release2.sh
index c9cb6f022..131cf8f3f 100755
--- a/qt6-after/qt6-migrated-legatus/new_docker_build_release2.sh
+++ b/qt6-after/qt6-migrated-legatus/new_docker_build_release2.sh
@@ -565,6 +565,9 @@ build_group "GROUP6 (Tools/AP9)" "${BUILD_GROUP6}" "${GROUP6_TARGETS[@]}"
 if [[ "${RUN_CTEST}" == "ON" ]] && [[ "${TESTS_ONLY}" != "ON" ]]; then
   log_info "Running ctest..."
   cd "${BUILD_DIR}"
+  # GUI test executables need a Qt platform plugin; the container is
+  # headless, so use the offscreen plugin (xcb would abort without a display).
+  export QT_QPA_PLATFORM="${QT_QPA_PLATFORM:-offscreen}"
   ctest --output-on-failure -j$(nproc) || log_info "Some tests failed (continuing)"
   cd ..
 fi
@@ -606,7 +609,10 @@ if [[ "${RUN_JENKINS_BUILDER}" == "ON" ]]; then
       --version "${LTS_VERSION}" \
       --output_dir "${DOCKER_MOUNT_ROOT}/rpms/${PROJECT}/${OS_VERSION}/" \
       --source_dir "${STAGED_SOURCE_DIR}" \
-      --cmake_build_flags "-DUSE_IPO=ON -DUSE_UNITY_BUILD=ON -DGUEZ_MODE=${GUEZ_MODE} -DBUILD_WLS=ON -DPostgreSQL_TYPE_INCLUDE_DIR=/usr/include/postgresql/ -DRELEASE_BUILD=ON" \
+      # -DBUILD_RTI=ON is required: the full-tree DEB build compiles RTI
+      # codegen consumers (e.g. svcPdmCommon -> pdm_enums.hpp) whose
+      # BUILD_RTI=OFF stubs were removed as "forbidden OFF variants".
+      --cmake_build_flags "-DUSE_IPO=ON -DUSE_UNITY_BUILD=ON -DGUEZ_MODE=${GUEZ_MODE} -DBUILD_WLS=ON -DPostgreSQL_TYPE_INCLUDE_DIR=/usr/include/postgresql/ -DBUILD_RTI=ON -DRELEASE_BUILD=ON" \
       --build_number "${BUILD_NUMBER}" \
       --release_scope; then
     log_info "Package build completed successfully"