--- ./CMakeLists.txt	2019-02-26 11:59:15.276962751 +0100
+++ ./CMakeLists.txt.new	2019-02-26 11:59:26.660962707 +0100
@@ -137,9 +137,10 @@
 ENDIF()
 
 ## Installation of the doc
+set(MEDFILE_DOC_DIRECTORY ${CMAKE_INSTALL_PREFIX}/share/doc/med-fichier-${MED_STR_VERSION} CACHE PATH "install dir for documentation")
 IF(MEDFILE_INSTALL_DOC  OR MEDFILE_BUILD_DOC)
-  INSTALL(DIRECTORY doc/html.dox/ DESTINATION ${CMAKE_INSTALL_PREFIX}/share/doc/med-fichier-${MED_STR_VERSION} REGEX "Makefile*" EXCLUDE PATTERN "*.am" EXCLUDE)
-  INSTALL(DIRECTORY doc/gif doc/jpg doc/png DESTINATION ${CMAKE_INSTALL_PREFIX}/share/doc/med-fichier-${MED_STR_VERSION} FILES_MATCHING PATTERN "*.gif" PATTERN "*.jpg" PATTERN "*.svg" PATTERN "*.png")
+  INSTALL(DIRECTORY doc/html.dox/ DESTINATION ${MEDFILE_DOC_DIRECTORY} REGEX "Makefile*" EXCLUDE PATTERN "*.am" EXCLUDE)
+  INSTALL(DIRECTORY doc/gif doc/jpg doc/png DESTINATION ${MEDFILE_DOC_DIRECTORY} FILES_MATCHING PATTERN "*.gif" PATTERN "*.jpg" PATTERN "*.svg" PATTERN "*.png")
 ENDIF()
 
 #######################