diff --git a/test/ruby/test_keyword.rb b/test/ruby/test_keyword.rb
index 9aca787dff..bc816751fd 100644
--- a/test/ruby/test_keyword.rb
+++ b/test/ruby/test_keyword.rb
@@ -4432,6 +4432,24 @@ class TestKeywordArgumentsSymProcRefinements < Test::Unit::TestCase
     assert_equal({one: 1, two: 2}, f.call(one:, two:))
   end
 
+  def m_bug20570(*a, **nil)
+    a
+  end
+
+  def test_splat_arg_with_prohibited_keyword
+    assert_equal([], m_bug20570(*[]))
+    assert_equal([1], m_bug20570(*[1]))
+    assert_equal([1, 2], m_bug20570(*[1, 2]))
+    h = nil
+    assert_equal([], m_bug20570(*[], **h))
+    assert_equal([1], m_bug20570(*[1], **h))
+    assert_equal([1, 2], m_bug20570(*[1, 2], **h))
+
+    assert_equal([], m_bug20570(*[], **nil))
+    assert_equal([1], m_bug20570(*[1], **nil))
+    assert_equal([1, 2], m_bug20570(*[1, 2], **nil))
+  end
+
   private def one
     1
   end
diff --git a/version.h b/version.h
index dd442f5c6b..f7a72f688c 100644
--- a/version.h
+++ b/version.h
@@ -11,7 +11,7 @@
 # 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 93
+#define RUBY_PATCHLEVEL 94
 
 #include "ruby/version.h"
 #include "ruby/internal/abi.h"
diff --git a/vm_args.c b/vm_args.c
index 14ae550d2f..1b720a89c4 100644
--- a/vm_args.c
+++ b/vm_args.c
@@ -434,7 +434,10 @@ fill_keys_values(st_data_t key, st_data_t val, st_data_t ptr)
 static inline int
 ignore_keyword_hash_p(VALUE keyword_hash, const rb_iseq_t * const iseq, unsigned int * kw_flag, VALUE * converted_keyword_hash)
 {
-    if (!RB_TYPE_P(keyword_hash, T_HASH)) {
+    if (keyword_hash == Qnil) {
+        goto ignore;
+    }
+    else if (!RB_TYPE_P(keyword_hash, T_HASH)) {
         keyword_hash = rb_to_hash_type(keyword_hash);
     }
 
@@ -445,9 +448,17 @@ ignore_keyword_hash_p(VALUE keyword_hash, const rb_iseq_t * const iseq, unsigned
         keyword_hash = rb_hash_dup(keyword_hash);
     }
     *converted_keyword_hash = keyword_hash;
-    return !(ISEQ_BODY(iseq)->param.flags.has_kw) &&
-           !(ISEQ_BODY(iseq)->param.flags.has_kwrest) &&
-           RHASH_EMPTY_P(keyword_hash);
+
+    if (!(ISEQ_BODY(iseq)->param.flags.has_kw) &&
+        !(ISEQ_BODY(iseq)->param.flags.has_kwrest) &&
+        RHASH_EMPTY_P(keyword_hash)) {
+      ignore:
+        *kw_flag &= ~(VM_CALL_KW_SPLAT | VM_CALL_KW_SPLAT_MUT);
+        return 1;
+    }
+    else {
+        return 0;
+    }
 }
 
 static VALUE
@@ -577,7 +588,6 @@ setup_parameters_complex(rb_execution_context_t * const ec, const rb_iseq_t * co
                     arg_rest_dup(args);
                     rb_ary_pop(args->rest);
                     given_argc--;
-                    kw_flag &= ~(VM_CALL_KW_SPLAT | VM_CALL_KW_SPLAT_MUT);
                 }
                 else {
                     if (rest_last != converted_keyword_hash) {
@@ -608,7 +618,6 @@ setup_parameters_complex(rb_execution_context_t * const ec, const rb_iseq_t * co
             if (ignore_keyword_hash_p(last_arg, iseq, &kw_flag, &converted_keyword_hash)) {
                 args->argc--;
                 given_argc--;
-                kw_flag &= ~(VM_CALL_KW_SPLAT | VM_CALL_KW_SPLAT_MUT);
             }
             else {
                 if (!(kw_flag & VM_CALL_KW_SPLAT_MUT)) {