diff --git a/tools/build/mk/OptionalObsoleteFiles.inc b/tools/build/mk/OptionalObsoleteFiles.inc
--- a/tools/build/mk/OptionalObsoleteFiles.inc
+++ b/tools/build/mk/OptionalObsoleteFiles.inc
@@ -2073,11 +2073,6 @@
 OLD_DIRS+=usr/tests/usr.bin/dc
 .endif
 
-.if ${MK_GNU_DIFF} == no
-OLD_FILES+=usr/bin/diff3
-OLD_FILES+=usr/share/man/man1/diff3.1.gz
-.endif
-
 .if ${MK_GOOGLETEST} == no
 OLD_FILES+=usr/include/private/gmock/gmock-actions.h
 OLD_FILES+=usr/include/private/gmock/gmock-cardinalities.h
diff --git a/tools/build/options/WITHOUT_GNU_DIFF b/tools/build/options/WITHOUT_GNU_DIFF
--- a/tools/build/options/WITHOUT_GNU_DIFF
+++ b/tools/build/options/WITHOUT_GNU_DIFF
@@ -1,2 +1,5 @@
 Do not build GNU
-.Xr diff3 1 .
+.Xr diff3 1 ;
+build BSD
+.Xr diff3 1
+instead.
diff --git a/tools/build/options/WITH_GNU_DIFF b/tools/build/options/WITH_GNU_DIFF
--- a/tools/build/options/WITH_GNU_DIFF
+++ b/tools/build/options/WITH_GNU_DIFF
@@ -1,2 +1,4 @@
 Build and install GNU
+.Xr diff3 1
+instead of BSD
 .Xr diff3 1 .
diff --git a/usr.bin/Makefile b/usr.bin/Makefile
--- a/usr.bin/Makefile
+++ b/usr.bin/Makefile
@@ -212,6 +212,9 @@
 SUBDIR.${MK_OPENSSL}+=	bc
 SUBDIR.${MK_OPENSSL}+=	dc
 .endif
+.if ${MK_GNU_DIFF} == "no"
+SUBDIR+=		diff3
+.endif
 SUBDIR.${MK_HESIOD}+=	hesinfo
 SUBDIR.${MK_ICONV}+=	iconv
 SUBDIR.${MK_ICONV}+=	mkcsmapper