updated for version 7.3.501
Problem:    Error for "flush" not being defined when using Ruby command.
Solution:   Defined "flush" as a no-op method. (Kent Sibilev)
diff --git a/src/if_ruby.c b/src/if_ruby.c
index 5dc3285..3b5b93b 100644
--- a/src/if_ruby.c
+++ b/src/if_ruby.c
@@ -1238,6 +1238,11 @@
     return Qnil;
 }
 
+static VALUE f_nop(VALUE self)
+{
+    return Qnil;
+}
+
 static VALUE f_p(int argc, VALUE *argv, VALUE self UNUSED)
 {
     int i;
@@ -1259,6 +1264,7 @@
 
     rb_stdout = rb_obj_alloc(rb_cObject);
     rb_define_singleton_method(rb_stdout, "write", vim_message, 1);
+    rb_define_singleton_method(rb_stdout, "flush", f_nop, 0);
     rb_define_global_function("p", f_p, -1);
 }
 
diff --git a/src/version.c b/src/version.c
index 720e45a..94d429e 100644
--- a/src/version.c
+++ b/src/version.c
@@ -715,6 +715,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    501,
+/**/
     500,
 /**/
     499,