diff --git a/src/corelib/Qt5CoreConfigExtras.cmake.in b/src/corelib/Qt5CoreConfigExtras.cmake.in
index 155961bc9a6..440d5e92bb3 100644
--- a/src/corelib/Qt5CoreConfigExtras.cmake.in
+++ b/src/corelib/Qt5CoreConfigExtras.cmake.in
@@ -12,5 +12,7 @@ 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)
+if (NOT \"$$QT_NAMESPACE\" STREQUAL \"\")
+    list(APPEND Qt5Core_DEFINITIONS -DQT_NAMESPACE=$$QT_NAMESPACE)
+    list(APPEND Qt5Core_COMPILE_DEFINITIONS QT_NAMESPACE=$$QT_NAMESPACE)
+endif()