diff --git a/include/ruby/ruby.h b/include/ruby/ruby.h
index b467e6f547..23c196121c 100644
--- a/include/ruby/ruby.h
+++ b/include/ruby/ruby.h
@@ -1907,6 +1907,8 @@ RUBY_EXTERN VALUE rb_mMath;
 RUBY_EXTERN VALUE rb_mProcess;
 RUBY_EXTERN VALUE rb_mWaitReadable;
 RUBY_EXTERN VALUE rb_mWaitWritable;
+RUBY_EXTERN VALUE rb_mWarning;
+RUBY_EXTERN VALUE rb_cWarningBuffer;
 
 RUBY_EXTERN VALUE rb_cBasicObject;
 RUBY_EXTERN VALUE rb_cObject;