diff --git a/method.h b/method.h
index 2f4504bfec9fda..93a23b0e269eb2 100644
--- a/method.h
+++ b/method.h
@@ -102,8 +102,9 @@ static inline void
 METHOD_ENTRY_FLAGS_COPY(rb_method_entry_t *dst, const rb_method_entry_t *src)
 {
     dst->flags =
-      (dst->flags & ~(IMEMO_FL_USER0|IMEMO_FL_USER1|IMEMO_FL_USER2)) |
-        (src->flags & (IMEMO_FL_USER0|IMEMO_FL_USER1|IMEMO_FL_USER2));
+      (dst->flags & ~(IMEMO_FL_USER0|IMEMO_FL_USER1|IMEMO_FL_USER2
+      |IMEMO_FL_USER3)) |
+        (src->flags & (IMEMO_FL_USER0|IMEMO_FL_USER1|IMEMO_FL_USER2|IMEMO_FL_USER3));
 }
 
 typedef enum {
diff --git a/test/ruby/test_module.rb b/test/ruby/test_module.rb
index fa890c0e400cca..b5414d139ef94a 100644
--- a/test/ruby/test_module.rb
+++ b/test/ruby/test_module.rb
@@ -3176,6 +3176,50 @@ def test_module_name_in_singleton_method
     assert_match(/::Foo$/, mod.name, '[Bug #14895]')
   end
 
+  def test_iclass_memory_leak
+    # [Bug #19550]
+    assert_no_memory_leak([], <<~PREP, <<~CODE, rss: true)
+      code = proc do
+        mod = Module.new
+        Class.new do
+          include mod
+        end
+      end
+      1_000.times(&code)
+    PREP
+      3_000_000.times(&code)
+    CODE
+  end
+
+  def test_complemented_method_entry_memory_leak
+    # [Bug #19894]
+    assert_no_memory_leak([], <<~PREP, <<~CODE, rss: true)
+      code = proc do
+        $c = Class.new do
+          def foo; end
+        end
+
+        $m = Module.new do
+          refine $c do
+            def foo; end
+          end
+        end
+
+        Class.new do
+          using $m
+
+          def initialize
+            o = $c.new
+            o.method(:foo).unbind
+          end
+        end.new
+      end
+      1_000.times(&code)
+    PREP
+      100_000.times(&code)
+    CODE
+  end
+
   private
 
   def assert_top_method_is_private(method)
diff --git a/version.h b/version.h
index e462d5b4880cf3..676f7f8f09152e 100644
--- a/version.h
+++ b/version.h
@@ -11,11 +11,11 @@
 # define RUBY_VERSION_MINOR RUBY_API_VERSION_MINOR
 #define RUBY_VERSION_TEENY 4
 #define RUBY_RELEASE_DATE RUBY_RELEASE_YEAR_STR"-"RUBY_RELEASE_MONTH_STR"-"RUBY_RELEASE_DAY_STR
-#define RUBY_PATCHLEVEL 242
+#define RUBY_PATCHLEVEL 243
 
 #define RUBY_RELEASE_YEAR 2023
 #define RUBY_RELEASE_MONTH 10
-#define RUBY_RELEASE_DAY 10
+#define RUBY_RELEASE_DAY 17
 
 #include "ruby/version.h"
 
diff --git a/vm_method.c b/vm_method.c
index 7cebd2e3bce72f..f8f72f2cf2e3ab 100644
--- a/vm_method.c
+++ b/vm_method.c
@@ -651,11 +651,13 @@ rb_method_entry_create(ID called_id, VALUE klass, rb_method_visibility_t visi, c
 const rb_method_entry_t *
 rb_method_entry_clone(const rb_method_entry_t *src_me)
 {
-    rb_method_entry_t *me = rb_method_entry_alloc(src_me->called_id, src_me->owner, src_me->defined_class,
-                                                  method_definition_addref(src_me->def));
+    rb_method_entry_t *me = rb_method_entry_alloc(src_me->called_id, src_me->owner, src_me->defined_class, src_me->def);
     if (METHOD_ENTRY_COMPLEMENTED(src_me)) {
         method_definition_addref_complement(src_me->def);
     }
+    else {
+        method_definition_addref(src_me->def);
+    }
 
     METHOD_ENTRY_FLAGS_COPY(me, src_me);
     return me;
@@ -682,8 +684,8 @@ rb_method_entry_complement_defined_class(const rb_method_entry_t *src_me, ID cal
 	def = NULL;
     }
     else {
-	def = method_definition_addref_complement(def);
-    }
+        method_definition_addref_complement(def);
+}
     me = rb_method_entry_alloc(called_id, src_me->owner, defined_class, def);
     METHOD_ENTRY_FLAGS_COPY(me, src_me);
     METHOD_ENTRY_COMPLEMENTED_SET(me);