--- CMakeLists.txt.orig	2020-03-14 23:07:57 UTC
+++ CMakeLists.txt
@@ -21,7 +21,9 @@ include(DuneMacros)
 # start a dune project with information from dune.module
 dune_project()
 
+if (FREEBSD_INSTALL_DOCS)
 add_subdirectory(doc)
+endif()
 add_subdirectory(dune)
 add_subdirectory(test)