diff --git a/string.c b/string.c
index 8af608047a8e8f..9da57089649989 100644
--- a/string.c
+++ b/string.c
@@ -7231,6 +7231,8 @@ str_undump(VALUE str)
         }
     }
 
+    RB_GC_GUARD(str);
+
     return undumped;
 invalid_format:
     rb_raise(rb_eRuntimeError, "invalid dumped string; not wrapped with '\"' nor '\"...\".force_encoding(\"...\")' form");
diff --git a/test/ruby/test_string.rb b/test/ruby/test_string.rb
index 2ccabcbe80ab6d..42553cba8220b7 100644
--- a/test/ruby/test_string.rb
+++ b/test/ruby/test_string.rb
@@ -896,6 +896,17 @@ def test_undump
     }
   end
 
+  def test_undump_gc_compact_stress
+    a = S("Test") << 1 << 2 << 3 << 9 << 13 << 10
+    EnvUtil.under_gc_compact_stress do
+      assert_equal(a, S('"Test\\x01\\x02\\x03\\t\\r\\n"').undump)
+    end
+
+    EnvUtil.under_gc_compact_stress do
+      assert_equal(S("\u{ABCDE 10ABCD}"), S('"\\u{ABCDE 10ABCD}"').undump)
+    end
+  end
+
   def test_dup
     for frozen in [ false, true ]
       a = S("hello")