diff --git a/cmake/QtBaseGlobalTargets.cmake b/cmake/QtBaseGlobalTargets.cmake
index 15d2b887e20..1244ef4baf4 100644
--- a/cmake/QtBaseGlobalTargets.cmake
+++ b/cmake/QtBaseGlobalTargets.cmake
@@ -70,8 +70,25 @@ if(QT_WILL_INSTALL)
         DESTINATION "${__build_internals_install_dir}")
 endif()
 
+set(__build_internals_extra_files
+    "${CMAKE_CURRENT_SOURCE_DIR}/cmake/QtBuildInternals/QtBuildInternalsHelpers.cmake"
+)
+
+qt_copy_or_install(
+    FILES ${__build_internals_extra_files}
+    DESTINATION "${__build_internals_install_dir}")
+
+# In prefix builds we also need to copy the files into the build dir.
+if(QT_WILL_INSTALL)
+    foreach(__build_internals_file ${__build_internals_extra_files})
+        file(COPY "${__build_internals_file}" DESTINATION "${__build_internals_install_dir}")
+    endforeach()
+endif()
+
 set_property(DIRECTORY APPEND PROPERTY CMAKE_CONFIGURE_DEPENDS
-    "${CMAKE_CURRENT_SOURCE_DIR}/cmake/QtBuildInternals/${__build_internals_standalone_test_template_dir}/CMakeLists.txt")
+    "${CMAKE_CURRENT_SOURCE_DIR}/cmake/QtBuildInternals/${__build_internals_standalone_test_template_dir}/CMakeLists.txt"
+    ${__build_internals_extra_files}
+)
 
 qt_internal_create_toolchain_file()
 
diff --git a/cmake/QtBaseTopLevelHelpers.cmake b/cmake/QtBaseTopLevelHelpers.cmake
index 4b56e9a6646..febffae02d4 100644
--- a/cmake/QtBaseTopLevelHelpers.cmake
+++ b/cmake/QtBaseTopLevelHelpers.cmake
@@ -34,6 +34,23 @@ endmacro()
 
 macro(qt_internal_top_level_setup_after_project)
     qt_internal_top_level_setup_testing()
+    qt_internal_top_level_setup_cmake_and_export_namespace()
+endmacro()
+
+# Setting QT_CMAKE_EXPORT_NAMESPACE in the top-level scope is needed for any deferred call that is
+# run on the top-level scope (CMAKE_BINARY_DIR).
+macro(qt_internal_top_level_setup_cmake_and_export_namespace)
+    # Include the file that defines qt_internal_setup_cmake_and_export_namespace.
+    # We don't try to call find_package(QtBuildInternals) because that has a lot more side
+    # effects.
+    set(__qt6_build_internals_helpers_path
+        "${__qt6_qtbase_src_path}/cmake/QtBuildInternals/QtBuildInternalsHelpers.cmake")
+    if(NOT EXISTS "${__qt6_build_internals_helpers_path}")
+        message(FATAL_ERROR "Required file does not exist: '${__qt6_build_internals_helpers_path}'")
+    endif()
+    include("${__qt6_build_internals_helpers_path}")
+
+    qt_internal_setup_cmake_and_export_namespace()
 endmacro()
 
 macro(qt_internal_top_level_setup_testing)
diff --git a/cmake/QtBuildInternals/QtBuildInternalsConfig.cmake b/cmake/QtBuildInternals/QtBuildInternalsConfig.cmake
index 129f1ebb771..3a1920beb72 100644
--- a/cmake/QtBuildInternals/QtBuildInternalsConfig.cmake
+++ b/cmake/QtBuildInternals/QtBuildInternalsConfig.cmake
@@ -11,18 +11,7 @@ if(EXISTS "${CMAKE_CURRENT_LIST_DIR}/QtBuildInternalsExtra.cmake")
     include(${CMAKE_CURRENT_LIST_DIR}/QtBuildInternalsExtra.cmake)
 endif()
 
-macro(qt_internal_setup_cmake_and_export_namespace)
-    # The variables might have already been set in QtBuildInternalsExtra.cmake if the file is
-    # included while building a new module and not QtBase. In that case, stop overriding the value.
-    if(NOT INSTALL_CMAKE_NAMESPACE)
-        set(INSTALL_CMAKE_NAMESPACE "Qt${PROJECT_VERSION_MAJOR}"
-            CACHE STRING "CMake namespace [Qt${PROJECT_VERSION_MAJOR}]")
-    endif()
-    if(NOT QT_CMAKE_EXPORT_NAMESPACE)
-        set(QT_CMAKE_EXPORT_NAMESPACE "Qt${PROJECT_VERSION_MAJOR}"
-            CACHE STRING "CMake namespace used when exporting targets [Qt${PROJECT_VERSION_MAJOR}]")
-    endif()
-endmacro()
+include(${CMAKE_CURRENT_LIST_DIR}/QtBuildInternalsHelpers.cmake)
 
 macro(qt_set_up_build_internals_paths)
     # Set up the paths for the cmake modules located in the prefix dir. Prepend, so the paths are
diff --git a/cmake/QtBuildInternals/QtBuildInternalsHelpers.cmake b/cmake/QtBuildInternals/QtBuildInternalsHelpers.cmake
new file mode 100644
index 00000000000..aa845fd5c36
--- /dev/null
+++ b/cmake/QtBuildInternals/QtBuildInternalsHelpers.cmake
@@ -0,0 +1,15 @@
+# Copyright (C) 2025 The Qt Company Ltd.
+# SPDX-License-Identifier: BSD-3-Clause
+
+macro(qt_internal_setup_cmake_and_export_namespace)
+    # The variables might have already been set in QtBuildInternalsExtra.cmake if the file is
+    # included while building a new module and not QtBase. In that case, stop overriding the value.
+    if(NOT INSTALL_CMAKE_NAMESPACE)
+        set(INSTALL_CMAKE_NAMESPACE "Qt${PROJECT_VERSION_MAJOR}"
+            CACHE STRING "CMake namespace [Qt${PROJECT_VERSION_MAJOR}]")
+    endif()
+    if(NOT QT_CMAKE_EXPORT_NAMESPACE)
+        set(QT_CMAKE_EXPORT_NAMESPACE "Qt${PROJECT_VERSION_MAJOR}"
+            CACHE STRING "CMake namespace used when exporting targets [Qt${PROJECT_VERSION_MAJOR}]")
+    endif()
+endmacro()