diff --git a/src/if_ruby.c b/src/if_ruby.c

index 9e5890214..a8c8379b6 100644

--- a/src/if_ruby.c

+++ b/src/if_ruby.c

@@ -612,11 +612,13 @@ rb_check_type_stub(VALUE obj, int t)

 {

     dll_rb_check_type(obj, t);

 }

+#   if VIM_SIZEOF_INT < VIM_SIZEOF_LONG // 64 bits only

     unsigned long

 rb_num2uint_stub(VALUE x)

 {

     return dll_rb_num2uint(x);

 }

+#   endif

     void

 ruby_malloc_size_overflow_stub(size_t x, size_t y)

 {