diff --git a/CMakeLists.txt b/CMakeLists.txt
index d2d892aa1..8b81d7345 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,90 +1,99 @@
 cmake_minimum_required(VERSION 3.5)
 set(PIM_VERSION "5.12.40")
 
 project(KCalendarCore VERSION ${PIM_VERSION})
 
 # ECM setup
 set(KF5_MIN_VERSION "5.60.0")
 
 find_package(ECM ${KF5_MIN_VERSION} CONFIG REQUIRED)
 set(CMAKE_MODULE_PATH ${ECM_MODULE_PATH} ${KCalendarCore_SOURCE_DIR}/cmake)
 
 include(GenerateExportHeader)
 include(ECMGenerateHeaders)
 include(ECMGeneratePriFile)
 
 include(ECMSetupVersion)
 include(FeatureSummary)
 include(KDEInstallDirs)
 include(KDECMakeSettings)
 include(KDEFrameworkCompilerSettings NO_POLICY_SCOPE)
 include(ECMQtDeclareLoggingCategory)
 
+# TODO: remove for KF6
+option(KCALENDARCORE_NO_DEPRECATED_NAMESPACE "Disable deprecated KCalCore namespace" OFF)
+
 if(POLICY CMP0053)
   cmake_policy(SET CMP0053 NEW)
 endif()
 set(QT_REQUIRED_VERSION "5.11.0")
 
 set(KCALENDARCORE_LIB_VERSION ${PIM_VERSION})
 ecm_setup_version(PROJECT VARIABLE_PREFIX KCALCORE
   VERSION_HEADER "${KCalendarCore_BINARY_DIR}/kcalendarcore_version.h"
   PACKAGE_VERSION_FILE "${KCalendarCore_BINARY_DIR}/KF5CalendarCoreConfigVersion.cmake"
   SOVERSION 5
 )
 
 ########### Find packages ###########
 find_package(Qt5 ${QT_REQUIRED_VERSION} CONFIG REQUIRED Core Gui)
 
 set(LibIcal_MIN_VERSION "2.0")
 find_package(LibIcal ${LibIcal_MIN_VERSION})
 set_package_properties(LibIcal PROPERTIES TYPE REQUIRED)
 if(LibIcal_VERSION VERSION_GREATER "2.98")
   set(HAVE_ICAL_3 TRUE)
   add_definitions(-DUSE_ICAL_3)
 endif()
 
 ########### CMake Config Files ###########
 set(CMAKECONFIG_INSTALL_DIR "${KDE_INSTALL_CMAKEPACKAGEDIR}/KF5CalendarCore")
 
 configure_package_config_file(
   "${CMAKE_CURRENT_SOURCE_DIR}/KF5CalendarCoreConfig.cmake.in"
   "${CMAKE_CURRENT_BINARY_DIR}/KF5CalendarCoreConfig.cmake"
   INSTALL_DESTINATION ${CMAKECONFIG_INSTALL_DIR}
 )
 
 
 add_definitions(-DQT_DISABLE_DEPRECATED_BEFORE=0x060000)
 add_definitions(-DQT_NO_FOREACH)
 
 ########### Targets ###########
 add_subdirectory(src)
 
 if(BUILD_TESTING)
   find_package(Qt5 ${QT_REQUIRED_VERSION} CONFIG REQUIRED Test)
   add_subdirectory(autotests)
 endif()
 
 add_subdirectory(cmake)
 
 ########### Install Files ###########
 install(FILES
   "${CMAKE_CURRENT_BINARY_DIR}/KF5CalendarCoreConfig.cmake"
   "${CMAKE_CURRENT_BINARY_DIR}/KF5CalendarCoreConfigVersion.cmake"
   DESTINATION "${CMAKECONFIG_INSTALL_DIR}"
   COMPONENT Devel
 )
 
 install(EXPORT KF5CalendarCoreTargets
   DESTINATION "${CMAKECONFIG_INSTALL_DIR}"
   FILE KF5CalendarCoreTargets.cmake
   NAMESPACE KF5::
 )
 
 install(FILES
   ${CMAKE_CURRENT_BINARY_DIR}/kcalendarcore_version.h
   DESTINATION ${KDE_INSTALL_INCLUDEDIR_KF5} COMPONENT Devel
 )
+if (NOT KCALENDARCORE_NO_DEPRECATED_NAMESPACE)
+  install(FILES
+    ${CMAKE_CURRENT_BINARY_DIR}/kcalendarcore_version.h
+    DESTINATION ${KDE_INSTALL_INCLUDEDIR_KF5} COMPONENT Devel RENAME kcalcore_version.h
+  )
+endif()
 
 install(FILES kcalendarcore.renamecategories kcalendarcore.categories  DESTINATION  ${KDE_INSTALL_LOGGINGCATEGORIESDIR})
 
 feature_summary(WHAT ALL FATAL_ON_MISSING_REQUIRED_PACKAGES)
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 55c6b3541..02dad3b0a 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -1,155 +1,153 @@
 
 ########### next target ###############
 
 set(kcalcore_LIB_SRCS
   alarm.cpp
   attachment.cpp
   attendee.cpp
   calendar.cpp
   calfilter.cpp
   calformat.cpp
   calstorage.cpp
   compat.cpp
   customproperties.cpp
   duration.cpp
   event.cpp
   exceptions.cpp
   filestorage.cpp
   freebusy.cpp
   freebusycache.cpp
   freebusyperiod.cpp
   icalformat.cpp
   icalformat_p.cpp
   icaltimezones.cpp
   incidence.cpp
   incidencebase.cpp
   journal.cpp
   memorycalendar.cpp
   occurrenceiterator.cpp
   period.cpp
   person.cpp
   recurrence.cpp
   recurrencerule.cpp
   schedulemessage.cpp
   sorting.cpp
   todo.cpp
   utils.cpp
   vcalformat.cpp
   visitor.cpp
 )
 ecm_qt_declare_logging_category(kcalcore_LIB_SRCS HEADER kcalendarcore_debug.h IDENTIFIER KCALCORE_LOG CATEGORY_NAME org.kde.pim.kcalcore)
 
 add_library(KF5CalendarCore ${kcalcore_LIB_SRCS})
 
 generate_export_header(KF5CalendarCore BASE_NAME kcalendarcore)
 
 add_library(KF5::CalendarCore ALIAS KF5CalendarCore)
 
 # backward compatibility with the old name
-# TODO: remove for KF6
-option(KCALENDARCORE_NO_DEPRECATED_NAMESPACE "Disable deprecated KCalCore namespace" OFF)
 if (NOT KCALENDARCORE_NO_DEPRECATED_NAMESPACE)
     target_compile_definitions(KF5CalendarCore INTERFACE "-DKCalCore=KCalendarCore")
 endif()
 
 target_include_directories(KF5CalendarCore INTERFACE "$<INSTALL_INTERFACE:${KDE_INSTALL_INCLUDEDIR_KF5}/KCalendarCore>")
 target_include_directories(KF5CalendarCore PUBLIC "$<BUILD_INTERFACE:${KCalendarCore_SOURCE_DIR}/src;${KCalendarCore_BINARY_DIR}/src>")
 
 target_link_libraries(KF5CalendarCore
 PUBLIC
     Qt5::Core
 PRIVATE
     Qt5::Gui
     LibIcal
 )
 
 set_target_properties(KF5CalendarCore PROPERTIES
     VERSION ${KCALCORE_VERSION_STRING}
     SOVERSION ${KCALCORE_SOVERSION}
     EXPORT_NAME CalendarCore
 )
 
 install(TARGETS KF5CalendarCore EXPORT KF5CalendarCoreTargets ${KF5_INSTALL_TARGETS_DEFAULT_ARGS})
 
 ########### Generate Headers ###############
 set(kcalendarcore_headers
   Alarm
   Attachment
   Attendee
   CalFilter
   CalFormat
   CalStorage
   Calendar
   CustomProperties
   Duration
   Event
   Exceptions
   FileStorage
   FreeBusy
   FreeBusyCache
   FreeBusyPeriod
   ICalFormat
   Incidence
   IncidenceBase
   Journal
   MemoryCalendar
   OccurrenceIterator
   Period
   Person
   Recurrence
   RecurrenceRule
   ScheduleMessage
   Sorting
   Todo
   VCalFormat
   Visitor
 )
 
 ecm_generate_headers(KCalendarCore_CamelCase_HEADERS
   HEADER_NAMES
     ${kcalendarcore_headers}
   PREFIX KCalendarCore
   REQUIRED_HEADERS KCalendarCore_HEADERS
 )
 
 if (NOT KCALENDARCORE_NO_DEPRECATED_NAMESPACE)
   ecm_generate_headers(KCalCore_CamelCase_HEADERS
     HEADER_NAMES
       ${kcalendarcore_headers}
     PREFIX KCalCore
     REQUIRED_HEADERS KCalCore_HEADERS
   )
 endif()
 
 ########### install files ###############
 
 install(FILES
   ${CMAKE_CURRENT_BINARY_DIR}/kcalendarcore_export.h
   ${KCalendarCore_HEADERS}
   DESTINATION ${KDE_INSTALL_INCLUDEDIR_KF5}/KCalendarCore/kcalendarcore
   COMPONENT Devel
 )
 
 install(FILES
   ${KCalendarCore_CamelCase_HEADERS}
   DESTINATION ${KDE_INSTALL_INCLUDEDIR_KF5}/KCalendarCore/KCalendarCore
   COMPONENT Devel
 )
 
 if (NOT KCALENDARCORE_NO_DEPRECATED_NAMESPACE)
   install(FILES
     ${CMAKE_CURRENT_BINARY_DIR}/kcalendarcore_export.h
     ${KCalCore_HEADERS}
     DESTINATION ${KDE_INSTALL_INCLUDEDIR_KF5}/KCalendarCore/kcalcore
     COMPONENT Devel
   )
 
   install(FILES
     ${KCalCore_CamelCase_HEADERS}
     DESTINATION ${KDE_INSTALL_INCLUDEDIR_KF5}/KCalendarCore/KCalCore
     COMPONENT Devel
   )
 endif()
 
 ecm_generate_pri_file(BASE_NAME KCalendarCore LIB_NAME KF5CalendarCore DEPS "Core" FILENAME_VAR PRI_FILENAME INCLUDE_INSTALL_DIR ${KDE_INSTALL_INCLUDEDIR_KF5}/KCalendarCore/KCalendarCore)
 install(FILES ${PRI_FILENAME} DESTINATION ${ECM_MKSPECS_INSTALL_DIR})