diff --git a/lib/protoboeuf/codegen.rb b/lib/protoboeuf/codegen.rb
index a286fa4..12161ee 100644
--- a/lib/protoboeuf/codegen.rb
+++ b/lib/protoboeuf/codegen.rb
@@ -1613,7 +1613,6 @@ def required_fields(msg)
 
       def init_bitmask(msg)
         optionals = optional_fields
-        raise NotImplementedError if optionals.length >= 63
 
         if optionals.empty?
           ""
diff --git a/test/codegen_test.rb b/test/codegen_test.rb
index 85fa03f..a47dbd2 100644
--- a/test/codegen_test.rb
+++ b/test/codegen_test.rb
@@ -228,6 +228,24 @@ def test_optional_fields
       assert(Class.new { class_eval(gen.to_ruby) })
     end
 
+    def test_many_optional_fields
+      unit = parse_string(<<~EOPROTO)
+        syntax = "proto3";
+
+        message TestManyOptionalFields {
+          #{(1..99).map { |i| "optional int32 a#{i} = #{i};" }.join("\n")}
+        }
+      EOPROTO
+      gen = CodeGen.new(unit)
+      klass = Class.new { class_eval(gen.to_ruby) }
+
+      msg = klass::TestManyOptionalFields.new(a59: 0, a60: 1, a99: 1)
+      msg = klass::TestManyOptionalFields.decode(klass::TestManyOptionalFields.encode(msg))
+      refute_predicate(msg, :has_a59?)
+      assert_predicate(msg, :has_a60?)
+      assert_predicate(msg, :has_a99?)
+    end
+
     def test_enum_field
       unit = parse_string(<<~EOPROTO)
         syntax = "proto3";