diff --git a/ChangeLog b/ChangeLog
index 0e9e80831a..fc5bf28fd3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -27,6 +27,12 @@ Sat Apr 19 21:55:10 2003  Akinori MUSHA  <knu@iDaemons.org>
 
 	* ext/Setup*: Add zlib and remove bogus and obsolete entries.
 
+Sat Apr 19 14:47:07 2003  Yukihiro Matsumoto  <matz@ruby-lang.org>
+
+	* gc.c (rb_gc): use rb_gc_mark_maybe() to mark registered C
+	  addresses.  C variables may not hold valid reference to Ruby
+	  objects. [ruby-core:00975]
+
 Sat Apr 19 00:56:13 2003  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
 	* struct.c (rb_struct_eql): should compare values with "eql?".
diff --git a/gc.c b/gc.c
index ae7cff920d..9097225184 100644
--- a/gc.c
+++ b/gc.c
@@ -1236,7 +1236,7 @@ rb_gc()
 
     /* mark protected global variables */
     for (list = global_List; list; list = list->next) {
-	rb_gc_mark(*list->varptr);
+	rb_gc_mark_maybe(*list->varptr);
     }
     rb_mark_end_proc();
     rb_gc_mark_global_tbl();
diff --git a/lib/singleton.rb b/lib/singleton.rb
index 3c20c13253..147b04187c 100644
--- a/lib/singleton.rb
+++ b/lib/singleton.rb
@@ -156,7 +156,7 @@ module Singleton
                 @__instance__ = new
             ensure
                 if @__instance__
-                    def self.instance() @__instance__ end
+		    define_method(:instance) {@__instance__}
                 else
                     @__instance__ = nil
                 end