diff --git a/ext/erb/escape/escape.c b/ext/erb/escape/escape.c
index db2abd9..2a5903c 100644
--- a/ext/erb/escape/escape.c
+++ b/ext/erb/escape/escape.c
@@ -89,6 +89,10 @@ erb_escape_html(VALUE self, VALUE str)
 void
 Init_escape(void)
 {
+#ifdef HAVE_RB_EXT_RACTOR_SAFE
+    rb_ext_ractor_safe(true);
+#endif
+
     rb_cERB = rb_define_class("ERB", rb_cObject);
     rb_mEscape = rb_define_module_under(rb_cERB, "Escape");
     rb_define_module_function(rb_mEscape, "html_escape", erb_escape_html, 1);
diff --git a/ext/erb/escape/extconf.rb b/ext/erb/escape/extconf.rb
index 783e8c1..b211a97 100644
--- a/ext/erb/escape/extconf.rb
+++ b/ext/erb/escape/extconf.rb
@@ -4,5 +4,6 @@
 when 'jruby', 'truffleruby'
   File.write('Makefile', dummy_makefile($srcdir).join)
 else
+  have_func("rb_ext_ractor_safe", "ruby.h")
   create_makefile 'erb/escape'
 end