diff --git a/CMakeLists.txt b/CMakeLists.txt
index f678592..d8b2c70 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -225,7 +225,6 @@ add_custom_target (clang-tidy
 # Installation
 install (TARGETS xB xC xD DESTINATION ${CMAKE_INSTALL_BINDIR})
 install (FILES LICENSE DESTINATION ${CMAKE_INSTALL_DOCDIR})
-# XXX: our defaults for XDG_DATA_DIRS expect /usr/local/share or /usr/share
 install (DIRECTORY plugins/xB/
 	DESTINATION ${CMAKE_INSTALL_DATADIR}/xB/plugins USE_SOURCE_PERMISSIONS)
 install (DIRECTORY plugins/xC/
diff --git a/config.h.in b/config.h.in
index 7e68c14..6f3911f 100644
--- a/config.h.in
+++ b/config.h.in
@@ -3,6 +3,9 @@
 
 #define PROGRAM_VERSION "${project_version}"
 
+// We use the XDG Base Directory Specification, but may be installed anywhere.
+#define PROJECT_DATADIR "${CMAKE_INSTALL_FULL_DATADIR}"
+
 #cmakedefine HAVE_READLINE
 #cmakedefine HAVE_EDITLINE
 #cmakedefine HAVE_LUA
diff --git a/xB.c b/xB.c
index f7c076b..3713724 100644
--- a/xB.c
+++ b/xB.c
@@ -1019,6 +1019,7 @@ plugin_resolve_relative_filename (const char *filename)
 {
 	struct strv paths = strv_make ();
 	get_xdg_data_dirs (&paths);
+	strv_append (&paths, PROJECT_DATADIR);
 	char *result = resolve_relative_filename_generic
 		(&paths, PROGRAM_NAME "/plugins/", filename);
 	strv_free (&paths);
diff --git a/xC.c b/xC.c
index 211f3e0..eb09053 100644
--- a/xC.c
+++ b/xC.c
@@ -11540,6 +11540,7 @@ plugin_resolve_relative_filename (const char *filename)
 {
 	struct strv paths = strv_make ();
 	get_xdg_data_dirs (&paths);
+	strv_append (&paths, PROJECT_DATADIR);
 	char *result = resolve_relative_filename_generic
 		(&paths, PROGRAM_NAME "/plugins/", filename);
 	strv_free (&paths);