--- CMakeLists.txt.orig	2021-01-21 11:28:09 UTC
+++ CMakeLists.txt
@@ -24,6 +24,12 @@ include(CheckIncludeFiles)
 include_directories("/usr/local/include")
 link_directories("/usr/local/lib")
 
+
+if (NOT DEFINED CMAKE_INSTALL_SYSCONFDIR )
+	set (CMAKE_INSTALL_SYSCONFDIR ${CMAKE_INSTALL_PREFIX}/etc)
+endif()
+set (SYSCONFDIR ${CMAKE_INSTALL_SYSCONFDIR}/iked)
+
 if (CMAKE_SYSTEM_NAME MATCHES "Darwin")
 	include_directories("/usr/local/opt/openssl@1.1/include")
 	link_directories("/usr/local/opt/openssl@1.1/lib")
@@ -32,8 +38,8 @@ elseif(CMAKE_SYSTEM_NAME MATCHES "OpenBSD")
 	add_definitions(-DHAVE_ATTRIBUTE__DEAD__)
 	add_definitions(-DHAVE_SOCKADDR_SA_LEN)
 elseif(CMAKE_SYSTEM_NAME MATCHES "FreeBSD")
-	add_definitions(-DIKED_CONFIG="/usr/local/etc/iked.conf")
-	add_definitions(-DIKED_CA="/usr/local/etc/iked/")
+	add_definitions(-DIKED_CONFIG="${CMAKE_INSTALL_SYSCONFDIR}/iked.conf")
+	add_definitions(-DIKED_CA="${SYSCONFDIR}/")
 elseif(CMAKE_SYSTEM_NAME MATCHES "Linux")
 	add_definitions(-D_GNU_SOURCE)
 	add_definitions(-D_DEFAULT_SOURCE)