diff --git a/ext/hbsdctl.rb/hbsdctl.c b/ext/hbsdctl.rb/hbsdctl.c
index 9eebca7..3b25621 100644
--- a/ext/hbsdctl.rb/hbsdctl.c
+++ b/ext/hbsdctl.rb/hbsdctl.c
@@ -79,7 +79,6 @@ Init_hbsdctl(void)
         rb_cFeature = rb_const_get(rb_mControl, rb_intern("Feature")),
         rb_mFFI     = rb_const_get(rb_mControl, rb_intern("FFI"));
 
-  rb_define_const(rb_mControl, "SysDef", INT2NUM(-1));
   rb_define_const(rb_mControl, "Disable", INT2NUM(0));
   rb_define_const(rb_mControl, "Enable", INT2NUM(1));
   rb_define_singleton_method(rb_mFFI, "available_features", ffi_available_features, 0);
diff --git a/lib/bsd/control/feature.rb b/lib/bsd/control/feature.rb
index d3b576e..1324a90 100644
--- a/lib/bsd/control/feature.rb
+++ b/lib/bsd/control/feature.rb
@@ -40,21 +40,6 @@ module BSD::Control
       set!(path, BSD::Control::Disable)
     end
 
-    ##
-    # Restore system defaults.
-    #
-    # @param [String] path
-    #  The path to a file.
-    #
-    # @raise [BSD::Control::Error]
-    #  When the operation fails.
-    #
-    # @return [Boolean]
-    #  Returns true on success.
-    def sysdef!(path)
-      set!(path, BSD::Control::SysDef)
-    end
-
     # @endgroup
 
     ##