diff --git a/benchmark/object_class.yml b/benchmark/object_class.yml
new file mode 100644
index 00000000000000..1e5409d1e2dfab
--- /dev/null
+++ b/benchmark/object_class.yml
@@ -0,0 +1,40 @@
+prelude: |
+  def get_class(obj)
+    i = 10_000
+    while i > 0
+      i -= 1
+      # 100 times per loop
+      obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class;
+      obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class;
+      obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class;
+      obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class;
+      obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class;
+      obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class;
+      obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class;
+      obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class;
+      obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class;
+      obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class;
+      obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class; obj.class;
+    end
+  end
+
+  class Obj
+  end
+  obj = Obj.new
+
+  singleton = Obj.new
+  def singleton.bar
+  end
+
+  extended = Obj.new
+  2.times do
+    extended.extend Module.new
+  end
+
+  immediate = 1.4
+benchmark:
+  obj: get_class(obj)
+  extended: get_class(extended)
+  singleton: get_class(singleton)
+  immediate: get_class(immediate)
+loop_count: 1000
diff --git a/class.c b/class.c
index 24f61fd023e5fd..472095617c1e8a 100644
--- a/class.c
+++ b/class.c
@@ -62,8 +62,8 @@
  * 0:    RCLASS_IS_ROOT
  *           The class has been added to the VM roots. Will always be marked and pinned.
  *           This is done for classes defined from C to allow storing them in global variables.
- * 1:    RMODULE_IS_REFINEMENT
- *           Module is used for refinements.
+ * 1:    <reserved>
+ *          Ensures that RUBY_FL_SINGLETON is never set on a T_MODULE. See `rb_class_real`.
  * 2:    RCLASS_PRIME_CLASSEXT_PRIME_WRITABLE
  *           This module's prime classext is the only classext and writable from any namespaces.
  *           If unset, the prime classext is writable only from the root namespace.
@@ -71,6 +71,8 @@
  *           Module has been initialized.
  * 4:    RCLASS_NAMESPACEABLE
  *           Is a builtin class that may be namespaced. It larger than a normal class.
+ * 5:    RMODULE_IS_REFINEMENT
+ *           Module is used for refinements.
  */
 
 #define METACLASS_OF(k) RBASIC(k)->klass
diff --git a/kernel.rb b/kernel.rb
index 888ef0c531d7e6..5d596c889258c9 100644
--- a/kernel.rb
+++ b/kernel.rb
@@ -17,7 +17,7 @@ module Kernel
   #
   def class
     Primitive.attr! :leaf
-    Primitive.cexpr! 'rb_obj_class(self)'
+    Primitive.cexpr! 'rb_obj_class_must(self)'
   end
 
   #
diff --git a/object.c b/object.c
index a7def50cd7a068..6aa9c27f9dd876 100644
--- a/object.c
+++ b/object.c
@@ -278,12 +278,32 @@ rb_obj_not_equal(VALUE obj1, VALUE obj2)
     return rb_obj_not(result);
 }
 
+static inline VALUE
+fake_class_p(VALUE klass)
+{
+    RUBY_ASSERT(klass);
+    RUBY_ASSERT(RB_TYPE_P(klass, T_CLASS) || RB_TYPE_P(klass, T_MODULE) || RB_TYPE_P(klass, T_ICLASS));
+    STATIC_ASSERT(t_iclass_overlap_t_class, !(T_CLASS & T_ICLASS));
+    STATIC_ASSERT(t_iclass_overlap_t_module, !(T_MODULE & T_ICLASS));
+
+    return FL_TEST_RAW(klass, T_ICLASS | FL_SINGLETON);
+}
+
+static inline VALUE
+class_real(VALUE cl)
+{
+    RUBY_ASSERT(cl);
+    while (RB_UNLIKELY(fake_class_p(cl))) {
+        cl = RCLASS_SUPER(cl);
+    }
+    return cl;
+}
+
 VALUE
 rb_class_real(VALUE cl)
 {
-    while (cl &&
-        (RCLASS_SINGLETON_P(cl) || BUILTIN_TYPE(cl) == T_ICLASS)) {
-        cl = RCLASS_SUPER(cl);
+    if (cl) {
+        cl = class_real(cl);
     }
     return cl;
 }
@@ -291,7 +311,17 @@ rb_class_real(VALUE cl)
 VALUE
 rb_obj_class(VALUE obj)
 {
-    return rb_class_real(CLASS_OF(obj));
+    VALUE cl = CLASS_OF(obj);
+    if (cl) {
+        cl = class_real(cl);
+    }
+    return cl;
+}
+
+static inline VALUE
+rb_obj_class_must(VALUE obj)
+{
+    return class_real(CLASS_OF(obj));
 }
 
 /*