Index: UPDATING
===================================================================
--- UPDATING
+++ UPDATING
@@ -31,6 +31,13 @@
 	disable the most expensive debugging functionality run
 	"ln -s 'abort:false,junk:false' /etc/malloc.conf".)
 
+201510xx:
+	Debug data files are now built by default with 'make buildworld' and
+	installed with 'make installworld'. This facilitates debugging but
+	requires more disk space both during the build and for the installed
+	world. Debug files may be disabled by setting WITHOUT_DEBUG_FILES=yes
+	in src.conf(5).
+
 20151020:
 	Qlogic 24xx/25xx firmware images were updated from 5.5.0 to 7.3.0.
 	Kernel modules isp_2400_multi and isp_2500_multi were removed and
Index: share/mk/bsd.opts.mk
===================================================================
--- share/mk/bsd.opts.mk
+++ share/mk/bsd.opts.mk
@@ -50,6 +50,7 @@
 
 __DEFAULT_YES_OPTIONS = \
     ASSERT_DEBUG \
+    DEBUG_FILES \
     DOCCOMPRESS \
     INCLUDES \
     INSTALLLIB \
@@ -67,7 +68,6 @@
 
 __DEFAULT_NO_OPTIONS = \
     CTF \
-    DEBUG_FILES \
     INSTALL_AS_USER \
     STALE_STAGED