diff --git a/share/mk/src.opts.mk b/share/mk/src.opts.mk
--- a/share/mk/src.opts.mk
+++ b/share/mk/src.opts.mk
@@ -296,9 +296,9 @@
 .include <bsd.compiler.mk>
 
 .if ${__T} == "i386" || ${__T} == "amd64"
-__DEFAULT_NO_OPTIONS += FDT
+__DEFAULT_NO_OPTIONS+=FDT
 .else
-__DEFAULT_YES_OPTIONS += FDT
+__DEFAULT_YES_OPTIONS+=FDT
 .endif
 
 .if ${__T:Marm*} == "" && ${__T:Mriscv64*} == ""
@@ -519,8 +519,4 @@
 .endif
 .endfor
 
-#
-# Set defaults for the MK_*_SUPPORT variables.
-#
-
 .endif #  !target(__<src.opts.mk>__)