diff --git a/gc/mmtk/src/scanning.rs b/gc/mmtk/src/scanning.rs
index be834bdd0bde95..355a2e7759584a 100644
--- a/gc/mmtk/src/scanning.rs
+++ b/gc/mmtk/src/scanning.rs
@@ -4,6 +4,7 @@ use crate::upcalls;
 use crate::utils::ChunkedVecCollector;
 use crate::Ruby;
 use crate::RubySlot;
+use mmtk::memory_manager;
 use mmtk::scheduler::GCWork;
 use mmtk::scheduler::GCWorker;
 use mmtk::scheduler::WorkBucketStage;
@@ -53,6 +54,19 @@ impl Scanning<Ruby> for VMScanning {
                 mmtk::memory_manager::is_mmtk_object(target_object.to_raw_address()).is_some(),
                 "Destination is not an MMTk object. Src: {object} dst: {target_object}"
             );
+
+            debug_assert!(
+                // If we are in a moving GC, all objects should be pinned by PinningRegistry.
+                // If it is requested that target_object be pinned but it is not pinned, then
+                // it is a bug because it could be moved.
+                if crate::mmtk().get_plan().current_gc_may_move_object() && pin {
+                    memory_manager::is_pinned(target_object)
+                } else {
+                    true
+                },
+                "Object {object} is trying to pin {target_object}"
+            );
+
             let forwarded_target = object_tracer.trace_object(target_object);
             if forwarded_target != target_object {
                 trace!("  Forwarded target {target_object} -> {forwarded_target}");
diff --git a/hash.c b/hash.c
index c4e8512f64c458..b0de8e943355af 100644
--- a/hash.c
+++ b/hash.c
@@ -1497,6 +1497,10 @@ rb_hash_new_capa(long capa)
 static VALUE
 hash_copy(VALUE ret, VALUE hash)
 {
+    if (rb_hash_compare_by_id_p(hash)) {
+        rb_gc_register_pinning_obj(ret);
+    }
+
     if (RHASH_AR_TABLE_P(hash)) {
         if (RHASH_AR_TABLE_P(ret)) {
             ar_copy(ret, hash);
diff --git a/test/ruby/test_call.rb b/test/ruby/test_call.rb
index 1b30ed34d8826f..dd1936c4e2689e 100644
--- a/test/ruby/test_call.rb
+++ b/test/ruby/test_call.rb
@@ -123,6 +123,25 @@ def self.f(*a); a end
    assert_equal([1, 2, {kw: 3}], f(*a, kw: 3))
   end
 
+  def test_forward_argument_init
+    o = Object.new
+    def o.simple_forward_argument_init(a=eval('b'), b=1)
+      [a, b]
+    end
+
+    def o.complex_forward_argument_init(a=eval('b'), b=eval('kw'), kw: eval('kw2'), kw2: 3)
+      [a, b, kw, kw2]
+    end
+
+    def o.keyword_forward_argument_init(a: eval('b'), b: eval('kw'), kw: eval('kw2'), kw2: 3)
+      [a, b, kw, kw2]
+    end
+
+    assert_equal [nil, 1], o.simple_forward_argument_init
+    assert_equal [nil, nil, 3, 3], o.complex_forward_argument_init
+    assert_equal [nil, nil, 3, 3], o.keyword_forward_argument_init
+  end
+
   def test_call_bmethod_proc
     pr = proc{|sym| sym}
     define_singleton_method(:a, &pr)
diff --git a/thread_sync.c b/thread_sync.c
index 72341762399a8f..3227bab8435b1a 100644
--- a/thread_sync.c
+++ b/thread_sync.c
@@ -1043,12 +1043,8 @@ rb_queue_initialize(int argc, VALUE *argv, VALUE self)
             initial_capa *= 2;
         }
         ring_buffer_init(q, initial_capa);
-
-        const VALUE *initial_ptr = RARRAY_CONST_PTR(initial);
-
-        for (long index = 0; index < len; index++) {
-            ring_buffer_push(self, q, initial_ptr[index]);
-        }
+        MEMCPY(q->buffer, RARRAY_CONST_PTR(initial), VALUE, len);
+        q->len = len;
     }
     else {
         ring_buffer_init(q, QUEUE_INITIAL_CAPA);
diff --git a/vm_args.c b/vm_args.c
index 8d4042e35566ae..458710e59e3688 100644
--- a/vm_args.c
+++ b/vm_args.c
@@ -245,7 +245,6 @@ args_setup_opt_parameters(struct args_info *args, int opt_max, VALUE *locals)
         i = opt_max;
     }
     else {
-        int j;
         i = args->argc;
         args->argc = 0;
 
@@ -257,11 +256,6 @@ args_setup_opt_parameters(struct args_info *args, int opt_max, VALUE *locals)
                 locals[i] = argv[args->rest_index];
             }
         }
-
-        /* initialize by nil */
-        for (j=i; j<opt_max; j++) {
-            locals[j] = Qnil;
-        }
     }
 
     return i;