diff --git a/gc.c b/gc.c
index 38f0fd2ce1..2687dbb5a6 100644
--- a/gc.c
+++ b/gc.c
@@ -12117,10 +12117,26 @@ struct wmap_iter_arg {
     VALUE value;
 };
 
+static VALUE
+wmap_inspect_append(rb_objspace_t *objspace, VALUE str, VALUE obj)
+{
+    if (SPECIAL_CONST_P(obj)) {
+        return rb_str_append(str, rb_inspect(obj));
+    }
+    else if (wmap_live_p(objspace, obj)) {
+        return rb_str_append(str, rb_any_to_s(obj));
+    }
+    else {
+        return rb_str_catf(str, "#<collected:%p>", (void*)obj);
+    }
+}
+
 static int
 wmap_inspect_i(st_data_t key, st_data_t val, st_data_t arg)
 {
-    VALUE str = (VALUE)arg;
+    struct wmap_iter_arg *argp = (struct wmap_iter_arg *)arg;
+    rb_objspace_t *objspace = argp->objspace;
+    VALUE str = argp->value;
     VALUE k = (VALUE)key, v = (VALUE)val;
 
     if (RSTRING_PTR(str)[0] == '#') {
@@ -12130,11 +12146,9 @@ wmap_inspect_i(st_data_t key, st_data_t val, st_data_t arg)
 	rb_str_cat2(str, ": ");
 	RSTRING_PTR(str)[0] = '#';
     }
-    k = SPECIAL_CONST_P(k) ? rb_inspect(k) : rb_any_to_s(k);
-    rb_str_append(str, k);
+    wmap_inspect_append(objspace, str, k);
     rb_str_cat2(str, " => ");
-    v = SPECIAL_CONST_P(v) ? rb_inspect(v) : rb_any_to_s(v);
-    rb_str_append(str, v);
+    wmap_inspect_append(objspace, str, v);
 
     return ST_CONTINUE;
 }
@@ -12145,11 +12159,14 @@ wmap_inspect(VALUE self)
     VALUE str;
     VALUE c = rb_class_name(CLASS_OF(self));
     struct weakmap *w;
+    struct wmap_iter_arg args;
 
     TypedData_Get_Struct(self, struct weakmap, &weakmap_type, w);
     str = rb_sprintf("-<%"PRIsVALUE":%p", c, (void *)self);
     if (w->wmap2obj) {
-	st_foreach(w->wmap2obj, wmap_inspect_i, str);
+	args.objspace = &rb_objspace;
+	args.value = str;
+	st_foreach(w->wmap2obj, wmap_inspect_i, (st_data_t)&args);
     }
     RSTRING_PTR(str)[0] = '#';
     rb_str_cat2(str, ">");
diff --git a/test/ruby/test_weakmap.rb b/test/ruby/test_weakmap.rb
index 3b9eef770a..46d8b50c03 100644
--- a/test/ruby/test_weakmap.rb
+++ b/test/ruby/test_weakmap.rb
@@ -73,6 +73,15 @@ class TestWeakMap < Test::Unit::TestCase
                  @wm.inspect)
   end
 
+  def test_inspect_garbage
+    1000.times do |i|
+      @wm[i] = Object.new
+      @wm.inspect
+    end
+    assert_match(/\A\#<#{@wm.class.name}:[^:]++:(?:\s\d+\s=>\s\#<(?:Object|collected):[^:<>]*+>(?:,|>\z))+/,
+                 @wm.inspect)
+  end
+
   def test_each
     m = __callee__[/test_(.*)/, 1]
     x1 = Object.new