diff --git a/bootstraptest/test_ractor.rb b/bootstraptest/test_ractor.rb
index cbf58383c7..f733877319 100644
--- a/bootstraptest/test_ractor.rb
+++ b/bootstraptest/test_ractor.rb
@@ -1379,4 +1379,19 @@ assert_equal "ok", %q{
   end
 }
 
+# Can yield back values while GC is sweeping [Bug #18117]
+assert_equal "ok", %q{
+  workers = (0...8).map do
+    Ractor.new do
+      loop do
+        10_000.times.map { Object.new }
+        Ractor.yield Time.now
+      end
+    end
+  end
+
+  1_000.times { idle_worker, tmp_reporter = Ractor.select(*workers) }
+  "ok"
+}
+
 end # if !ENV['GITHUB_WORKFLOW']
diff --git a/ractor.c b/ractor.c
index df9cbc307a..7d6fec76e0 100644
--- a/ractor.c
+++ b/ractor.c
@@ -2325,7 +2325,11 @@ obj_traverse_i(VALUE obj, struct obj_traverse_data *data)
                 .stop = false,
                 .data = data,
             };
-            rb_objspace_reachable_objects_from(obj, obj_traverse_reachable_i, &d);
+            RB_VM_LOCK_ENTER_NO_BARRIER();
+            {
+                rb_objspace_reachable_objects_from(obj, obj_traverse_reachable_i, &d);
+            }
+            RB_VM_LOCK_LEAVE_NO_BARRIER();
             if (d.stop) return 1;
         }
         break;
@@ -2635,7 +2639,11 @@ static int
 obj_refer_only_shareables_p(VALUE obj)
 {
     int cnt = 0;
-    rb_objspace_reachable_objects_from(obj, obj_refer_only_shareables_p_i, &cnt);
+    RB_VM_LOCK_ENTER_NO_BARRIER();
+    {
+        rb_objspace_reachable_objects_from(obj, obj_refer_only_shareables_p_i, &cnt);
+    }
+    RB_VM_LOCK_LEAVE_NO_BARRIER();
     return cnt == 0;
 }
 
diff --git a/version.h b/version.h
index 7f9cb6ada6..44efd8ff67 100644
--- a/version.h
+++ b/version.h
@@ -12,7 +12,7 @@
 # define RUBY_VERSION_MINOR RUBY_API_VERSION_MINOR
 #define RUBY_VERSION_TEENY 3
 #define RUBY_RELEASE_DATE RUBY_RELEASE_YEAR_STR"-"RUBY_RELEASE_MONTH_STR"-"RUBY_RELEASE_DAY_STR
-#define RUBY_PATCHLEVEL 127
+#define RUBY_PATCHLEVEL 128
 
 #define RUBY_RELEASE_YEAR 2021
 #define RUBY_RELEASE_MONTH 9