diff --git a/process.c b/process.c
index 5d16a3854a..fb31418e00 100644
--- a/process.c
+++ b/process.c
@@ -4353,6 +4353,13 @@ rb_call_proc__fork(void)
  *  This method is not for casual code but for application monitoring
  *  libraries. You can add custom code before and after fork events
  *  by overriding this method.
+ *
+ *  Note: Process.daemon may be implemented using fork(2) BUT does not go
+ *  through this method.
+ *  Thus, depending on your reason to hook into this method, you
+ *  may also want to hook into that one.
+ *  See {this issue}[https://bugs.ruby-lang.org/issues/18911] for a
+ *  more detailed discussion of this.
  */
 VALUE
 rb_proc__fork(VALUE _obj)