3 files changed, 8 insertions, 11 deletions
diff --git a/gc.c b/gc.c
index 4c8a042c1e..7663e82f41 100644
--- a/gc.c
+++ b/gc.c
@@ -4357,7 +4357,7 @@ gc_config_set(rb_execution_context_t *ec, VALUE self, VALUE hash)
 
     rb_gc_impl_config_set(objspace, hash);
 
-    return rb_gc_impl_config_get(objspace);
+    return Qnil;
 }
 
 static VALUE
diff --git a/gc.rb b/gc.rb
index a7620fd9ac..603520df53 100644
--- a/gc.rb
+++ b/gc.rb
@@ -312,17 +312,17 @@ module GC
   #     before setting this parameter to +false+.
   #
   def self.config hash = nil
-    return Primitive.gc_config_get unless hash
-
-    if(Primitive.cexpr!("RBOOL(RB_TYPE_P(hash, T_HASH))"))
+    if Primitive.cexpr!("RBOOL(RB_TYPE_P(hash, T_HASH))")
       if hash.include?(:implementation)
         raise ArgumentError, 'Attempting to set read-only key "Implementation"'
       end
 
       Primitive.gc_config_set hash
-    else
+    elsif hash != nil
       raise ArgumentError
     end
+
+    Primitive.gc_config_get
   end
 
   # call-seq:
diff --git a/test/ruby/test_gc.rb b/test/ruby/test_gc.rb
index 85022cbc4d..ccccd212b6 100644
--- a/test/ruby/test_gc.rb
+++ b/test/ruby/test_gc.rb
@@ -75,12 +75,9 @@ class TestGc < Test::Unit::TestCase
     GC.start
   end
 
-  def test_gc_config_setting_returns_nil_for_missing_keys
-    missing_value = GC.config(no_such_key: true)[:no_such_key]
-    assert_nil(missing_value)
-  ensure
-    GC.config(full_mark: true)
-    GC.start
+  def test_gc_config_setting_returns_config_hash
+    hash = GC.config(no_such_key: true)
+    assert_equal(GC.config, hash)
   end
 
   def test_gc_config_disable_major