diff --git a/docs/changes.xml b/docs/changes.xml
index c69523f9..a4db9ec5 100644
--- a/docs/changes.xml
+++ b/docs/changes.xml
@@ -50,6 +50,12 @@ points on a per-request basis during static file serving.
 </para>
 </change>
 
+<change type="feature">
+<para>
+compatibility with Ruby 3.0.
+</para>
+</change>
+
 <change type="bugfix">
 <para>
 a segmentation fault might have occurred in the PHP module if
diff --git a/src/ruby/nxt_ruby_stream_io.c b/src/ruby/nxt_ruby_stream_io.c
index 69bf289e..82ad3908 100644
--- a/src/ruby/nxt_ruby_stream_io.c
+++ b/src/ruby/nxt_ruby_stream_io.c
@@ -25,7 +25,9 @@ nxt_ruby_stream_io_input_init(void)
 {
     VALUE  stream_io;
 
-    stream_io = rb_define_class("NGINX_Unit_Stream_IO_Read", rb_cData);
+    stream_io = rb_define_class("NGINX_Unit_Stream_IO_Read", rb_cObject);
+
+    rb_undef_alloc_func(stream_io);
 
     rb_gc_register_address(&stream_io);
 
@@ -46,7 +48,9 @@ nxt_ruby_stream_io_error_init(void)
 {
     VALUE  stream_io;
 
-    stream_io = rb_define_class("NGINX_Unit_Stream_IO_Error", rb_cData);
+    stream_io = rb_define_class("NGINX_Unit_Stream_IO_Error", rb_cObject);
+
+    rb_undef_alloc_func(stream_io);
 
     rb_gc_register_address(&stream_io);