diff --git a/class.c b/class.c
index 4715e1b427..dc371c1970 100644
--- a/class.c
+++ b/class.c
@@ -445,6 +445,7 @@ copy_tables(VALUE clone, VALUE orig)
         rb_id_table_foreach(rb_cvc_tbl, cvc_table_copy, &ctx);
         RCLASS_CVC_TBL(clone) = rb_cvc_tbl_dup;
     }
+    rb_id_table_free(RCLASS_M_TBL(clone));
     RCLASS_M_TBL(clone) = 0;
     if (!RB_TYPE_P(clone, T_ICLASS)) {
         st_data_t id;
diff --git a/test/ruby/test_module.rb b/test/ruby/test_module.rb
index 425cbdf031..dd8cc471d0 100644
--- a/test/ruby/test_module.rb
+++ b/test/ruby/test_module.rb
@@ -3318,6 +3318,18 @@ class TestModule < Test::Unit::TestCase
     CODE
   end
 
+  def test_module_clone_memory_leak
+    # [Bug #19901]
+    assert_no_memory_leak([], <<~PREP, <<~CODE, rss: true)
+      code = proc do
+        Module.new.clone
+      end
+      1_000.times(&code)
+    PREP
+      1_000_000.times(&code)
+    CODE
+  end
+
   private
 
   def assert_top_method_is_private(method)
diff --git a/version.h b/version.h
index a05cefe39a..59923d31a9 100644
--- a/version.h
+++ b/version.h
@@ -11,7 +11,7 @@
 # define RUBY_VERSION_MINOR RUBY_API_VERSION_MINOR
 #define RUBY_VERSION_TEENY 2
 #define RUBY_RELEASE_DATE RUBY_RELEASE_YEAR_STR"-"RUBY_RELEASE_MONTH_STR"-"RUBY_RELEASE_DAY_STR
-#define RUBY_PATCHLEVEL 122
+#define RUBY_PATCHLEVEL 123
 
 #include "ruby/version.h"
 #include "ruby/internal/abi.h"