diff --git a/ext/etc/extconf.rb b/ext/etc/extconf.rb
index 2e28d58037..c4929c02d2 100644
--- a/ext/etc/extconf.rb
+++ b/ext/etc/extconf.rb
@@ -58,7 +58,7 @@ end
 # TODO: remove when dropping 2.7 support, as exported since 3.0
 have_func('rb_deprecate_constant(Qnil, "None")')
 
-have_func("rb_io_descriptor")
+have_func("rb_io_descriptor", "ruby/io.h")
 
 $distcleanfiles << "constdefs.h"