diff --git a/src/corelib/Qt5CoreConfigExtras.cmake.in b/src/corelib/Qt5CoreConfigExtras.cmake.in
index 057c8ff75e..155961bc9a 100644
--- a/src/corelib/Qt5CoreConfigExtras.cmake.in
+++ b/src/corelib/Qt5CoreConfigExtras.cmake.in
@@ -11,3 +11,6 @@ list(APPEND Qt5Core_INCLUDE_DIRS \"${_qt5_corelib_install_prefix}/mkspecs/defaul
 if (NOT \"$${CMAKE_ADD_FPIE_FLAGS}\" STREQUAL \"\")
     set(Qt5Core_COMPILE_FLAGS "-fPIE")
 endif()
+
+list(APPEND Qt5Core_DEFINITIONS -DQT_NAMESPACE=$$QT_NAMESPACE)
+list(APPEND Qt5Core_COMPILE_DEFINITIONS QT_NAMESPACE=$$QT_NAMESPACE)
diff --git a/tests/manual/cmake/fail4/CMakeLists.txt b/tests/manual/cmake/fail4/CMakeLists.txt
index dcd4b8bd65..2466e24d3a 100644
--- a/tests/manual/cmake/fail4/CMakeLists.txt
+++ b/tests/manual/cmake/fail4/CMakeLists.txt
@@ -7,6 +7,8 @@ find_package(Qt5Core REQUIRED)
 
 include_directories(${Qt5Core_INCLUDE_DIRS})
 
+add_definitions(${Qt5Core_DEFINITIONS})
+
 qt5_wrap_cpp(moc_files myobject.h)
 
 # Test options. The -binary option generates a binary to dlopen instead of
diff --git a/tests/manual/cmake/fail5/CMakeLists.txt b/tests/manual/cmake/fail5/CMakeLists.txt
index f82a62b626..9aedf4a008 100644
--- a/tests/manual/cmake/fail5/CMakeLists.txt
+++ b/tests/manual/cmake/fail5/CMakeLists.txt
@@ -7,6 +7,8 @@ find_package(Qt5Core REQUIRED)
 
 include_directories(${Qt5Core_INCLUDE_DIRS})
 
+add_definitions(${Qt5Core_DEFINITIONS})
+
 # Test options. The -i option removes the include "myobject.h" from the moc file
 # causing a compile failure. -> Options work
 qt5_wrap_cpp(moc_files myobject.h OPTIONS -i)
diff --git a/tests/manual/cmake/pass(needsquoting)6/CMakeLists.txt b/tests/manual/cmake/pass(needsquoting)6/CMakeLists.txt
index cc1a1bc588..fb971f9ebd 100644
--- a/tests/manual/cmake/pass(needsquoting)6/CMakeLists.txt
+++ b/tests/manual/cmake/pass(needsquoting)6/CMakeLists.txt
@@ -9,6 +9,8 @@ find_package(Qt5Widgets REQUIRED)
 
 include_directories(${Qt5Core_INCLUDE_DIRS} ${Qt5Gui_INCLUDE_DIRS} ${Qt5Widgets_INCLUDE_DIRS})
 
+add_definitions(${Qt5Core_DEFINITIONS})
+
 set(CMAKE_INCLUDE_CURRENT_DIR ON)
 
 qt5_wrap_cpp(moc_files mywidget.h)
diff --git a/tests/manual/cmake/pass2/CMakeLists.txt b/tests/manual/cmake/pass2/CMakeLists.txt
index ac1bb15846..a52744623e 100644
--- a/tests/manual/cmake/pass2/CMakeLists.txt
+++ b/tests/manual/cmake/pass2/CMakeLists.txt
@@ -7,6 +7,8 @@ find_package(Qt5Core REQUIRED)
 
 include_directories(${Qt5Core_INCLUDE_DIRS})
 
+add_definitions(${Qt5Core_DEFINITIONS})
+
 qt5_wrap_cpp(moc_files myobject.h)
 
 qt5_add_resources(rcc_files "pass2.qrc")
diff --git a/tests/manual/cmake/pass3/CMakeLists.txt b/tests/manual/cmake/pass3/CMakeLists.txt
index 11402e2e18..b836161813 100644
--- a/tests/manual/cmake/pass3/CMakeLists.txt
+++ b/tests/manual/cmake/pass3/CMakeLists.txt
@@ -8,6 +8,8 @@ find_package(Qt5Widgets REQUIRED)
 
 include_directories(${Qt5Widgets_INCLUDE_DIRS})
 
+add_definitions(${Qt5Core_DEFINITIONS})
+
 set(CMAKE_INCLUDE_CURRENT_DIR ON)
 
 qt5_wrap_cpp(moc_files mywidget.h)
diff --git a/tests/manual/cmake/pass7/CMakeLists.txt b/tests/manual/cmake/pass7/CMakeLists.txt
index f639c164ea..e7c9b46ead 100644
--- a/tests/manual/cmake/pass7/CMakeLists.txt
+++ b/tests/manual/cmake/pass7/CMakeLists.txt
@@ -6,5 +6,6 @@ project(pass7)
 find_package(Qt5Core REQUIRED)
 
 include_directories(${Qt5Core_INCLUDE_DIRS})
+add_definitions(${Qt5Core_DEFINITIONS})
 
 add_executable(myobject main.cpp)