diff --git a/ext/tk/lib/tk.rb b/ext/tk/lib/tk.rb
index 736a12fd26..9a15f09989 100644
--- a/ext/tk/lib/tk.rb
+++ b/ext/tk/lib/tk.rb
@@ -264,7 +264,7 @@ module TkComm
   end
   def uninstall_cmd(id)
     id = $1 if /rb_out (c\d+)/ =~ id
-    Tk_CMDTBL[id] = nil
+    Tk_CMDTBL.delete(id)
   end
   private :install_cmd, :uninstall_cmd
 
@@ -282,7 +282,7 @@ module TkComm
   end
 
   def uninstall_win()
-    Tk_WINDOWS[@path] = nil
+    Tk_WINDOWS.delete(@path)
   end
 
   class Event
@@ -2188,7 +2188,7 @@ module TkOption
         METHOD_TBL = {}
         ADD_METHOD = #{add}
         SAFE_MODE  = #{safe}
-        %w(#{func_str}).each{|f| METHOD_TBL[f.intern] = nil }
+        %w(#{func_str}).each{|f| METHOD_TBL.delete(f.intern) }
       end
     EOD
 
diff --git a/ext/tk/lib/tkafter.rb b/ext/tk/lib/tkafter.rb
index ec39d9957f..b7c21e7529 100644
--- a/ext/tk/lib/tkafter.rb
+++ b/ext/tk/lib/tkafter.rb
@@ -64,7 +64,7 @@ class TkAfter
 
   def set_next_callback(args)
     if @running == false || @proc_max == 0 || @do_loop == 0
-      Tk_CBTBL[@id] = nil ;# for GC
+      Tk_CBTBL.delete(@id) ;# for GC
       @running = false
       return
     end
@@ -72,7 +72,7 @@ class TkAfter
       if @do_loop < 0 || (@do_loop -= 1) > 0
 	@current_pos = 0
       else
-	Tk_CBTBL[@id] = nil ;# for GC
+	Tk_CBTBL.delete(@id) ;# for GC
 	@running = false
 	return
       end
@@ -272,7 +272,7 @@ class TkAfter
     @running = false
     tk_call 'after', 'cancel', @after_id if @after_id
     @after_id = nil
-    Tk_CBTBL[@id] = nil ;# for GC
+    Tk_CBTBL.delete(@id) ;# for GC
     self
   end
   alias stop cancel
diff --git a/ext/tk/lib/tkcanvas.rb b/ext/tk/lib/tkcanvas.rb
index 18febd2f13..4a5e4b45bb 100644
--- a/ext/tk/lib/tkcanvas.rb
+++ b/ext/tk/lib/tkcanvas.rb
@@ -504,7 +504,7 @@ class TkcTag<TkObject
 
   def delete
     @c.delete @id
-    CTagID_TBL[@cpath][@id] = nil if CTagID_TBL[@cpath]
+    CTagID_TBL[@cpath].delete(@id) if CTagID_TBL[@cpath]
   end
   alias remove  delete
   alias destroy delete
@@ -688,7 +688,7 @@ class TkcItem<TkObject
 
   def delete
     @c.delete @id
-    CItemID_TBL[@path][@id] = nil if CItemID_TBL[@path]
+    CItemID_TBL[@path].delete(@id) if CItemID_TBL[@path]
   end
   alias remove  delete
   alias destroy delete
@@ -763,7 +763,7 @@ class TkImage<TkObject
   end
 
   def delete
-    Tk_IMGTBL[@id] = nil if @id
+    Tk_IMGTBL.delete(@id) if @id
     tk_call('image', 'delete', @path)
   end
   def height
diff --git a/ext/tk/lib/tkfont.rb b/ext/tk/lib/tkfont.rb
index c56a8df506..d9eb8ecbed 100644
--- a/ext/tk/lib/tkfont.rb
+++ b/ext/tk/lib/tkfont.rb
@@ -564,7 +564,7 @@ class TkFont
   end
 
   def delete_core_tk4x
-    Tk_FontNameTBL[@id] = nil
+    Tk_FontNameTBL.delete(@id)
     Tk_FontUseTBL.delete_if{|key,value| value == self}
   end
 
@@ -581,7 +581,7 @@ class TkFont
       tk_call('font', 'delete', @compoundfont)
     rescue
     end
-    Tk_FontNameTBL[@id] = nil
+    Tk_FontNameTBL.delete(@id)
     Tk_FontUseTBL.delete_if{|key,value| value == self}
   end
 
@@ -610,7 +610,7 @@ class TkFont
 	    tk_call(w, 'configure', '-font', @latinfont)
 	  end
 	rescue
-	  Tk_FontUseTBL[w] = nil
+	  Tk_FontUseTBL.delete(w)
 	end
       end
     }
@@ -644,7 +644,7 @@ class TkFont
 	    tk_call(w, 'configure', '-kanjifont', @kanjifont)
 	  end
 	rescue
-	  Tk_FontUseTBL[w] = nil
+	  Tk_FontUseTBL.delete(w)
 	end
       end
     }
diff --git a/ext/tk/lib/tktext.rb b/ext/tk/lib/tktext.rb
index 952c05f566..dd4d649042 100644
--- a/ext/tk/lib/tktext.rb
+++ b/ext/tk/lib/tktext.rb
@@ -685,7 +685,7 @@ class TkTextTag<TkObject
 
   def destroy
     tk_call @t.path, 'tag', 'delete', @id
-    TTagID_TBL[@tpath][@id] = nil if CTagID_TBL[@tpath]
+    TTagID_TBL[@tpath].delete(@id) if CTagID_TBL[@tpath]
   end
 end
 
diff --git a/ext/tk/lib/tkvirtevent.rb b/ext/tk/lib/tkvirtevent.rb
index d3721e362e..f5dcdc9429 100644
--- a/ext/tk/lib/tkvirtevent.rb
+++ b/ext/tk/lib/tkvirtevent.rb
@@ -54,11 +54,11 @@ class TkVirtualEvent<TkObject
   def delete(*sequences)
     if sequences == []
       tk_call('event', 'delete', "<#{@id}>")
-      TkVirtualEventTBL[@id] = nil
+      TkVirtualEventTBL.delete(@id)
     else
       tk_call('event', 'delete', "<#{@id}>", 
 	      *(sequences.collect{|seq| "<#{tk_event_sequence(seq)}>"}) )
-      TkVirtualEventTBL[@id] = nil if info == []
+      TkVirtualEventTBL.delete(@id) if info == []
     end
     self
   end
diff --git a/gc.c b/gc.c
index 3ecac66aba..72cbfb626e 100644
--- a/gc.c
+++ b/gc.c
@@ -848,12 +848,12 @@ gc_sweep()
 {
     RVALUE *p, *pend, *final_list;
     int freed = 0;
-    int i, used = heaps_used;
+    int i, j;
 
     if (ruby_in_compile && ruby_parser_stack_on_heap()) {
 	/* should not reclaim nodes during compilation
            if yacc's semantic stack is not allocated on machine stack */
-	for (i = 0; i < used; i++) {
+	for (i = 0; i < heaps_used; i++) {
 	    p = heaps[i]; pend = p + heaps_limits[i];
 	    while (p < pend) {
 		if (!(p->as.basic.flags&FL_MARK) && BUILTIN_TYPE(p) == T_NODE)
@@ -869,8 +869,10 @@ gc_sweep()
     freelist = 0;
     final_list = deferred_final_list;
     deferred_final_list = 0;
-    for (i = 0; i < used; i++) {
+    for (i = 0; i < heaps_used; i++) {
 	int n = 0;
+	RVALUE *free = freelist;
+	RVALUE *final = final_list;
 
 	p = heaps[i]; pend = p + heaps_limits[i];
 	while (p < pend) {
@@ -899,7 +901,18 @@ gc_sweep()
 	    }
 	    p++;
 	}
-	freed += n;
+	if (n == heaps_limits[i] && freed + n > FREE_MIN) {
+	    RVALUE *pp;
+
+	    heaps_limits[i] = 0;
+	    for (pp = final_list; pp != final; pp = pp->as.free.next) {
+		p->as.free.flags |= FL_SINGLETON; /* freeing page mark */
+	    }
+	    freelist = free;	/* cancel this page from freelist */
+	}
+	else {
+	    freed += n;
+	}
     }
     if (freed < FREE_MIN) {
 	add_heap();
@@ -918,9 +931,23 @@ gc_sweep()
 	for (p = final_list; p; p = tmp) {
 	    tmp = p->as.free.next;
 	    run_final((VALUE)p);
-	    p->as.free.flags = 0;
-	    p->as.free.next = freelist;
-	    freelist = p;
+	    if (!FL_TEST(p, FL_SINGLETON)) { /* not freeing page */
+		p->as.free.flags = 0;
+		p->as.free.next = freelist;
+		freelist = p;
+	    }
+	}
+    }
+    for (i = j = 0; j < heaps_used; i++) {
+	if (heaps_limits[i] == 0) {
+	    free(heaps[i]);
+	    heaps_used--;
+	}
+	else {
+	    if (i != j) {
+		heaps[j] = heaps[i];
+	    }
+	    j++;
 	}
     }
 }
diff --git a/object.c b/object.c
index 71f5e99bdc..455d353b39 100644
--- a/object.c
+++ b/object.c
@@ -83,6 +83,14 @@ rb_class_real(cl)
     return cl;
 }
 
+VALUE
+rb_obj_type(obj)
+    VALUE obj;
+{
+    rb_warn("`type' is deprecated; use `class'");
+    return rb_class_real(CLASS_OF(obj));
+}
+
 VALUE
 rb_obj_class(obj)
     VALUE obj;
@@ -1292,7 +1300,7 @@ Init_Object()
     rb_define_method(rb_mKernel, "hash", rb_obj_id, 0);
     rb_define_method(rb_mKernel, "id", rb_obj_id, 0);
     rb_define_method(rb_mKernel, "__id__", rb_obj_id, 0);
-    rb_define_method(rb_mKernel, "type", rb_obj_class, 0);
+    rb_define_method(rb_mKernel, "type", rb_obj_type, 0);
     rb_define_method(rb_mKernel, "class", rb_obj_class, 0);
 
     rb_define_method(rb_mKernel, "clone", rb_obj_clone, 0);