diff --git a/source/support.tex b/source/support.tex
index 203a1bf45f..b09401313e 100644
--- a/source/support.tex
+++ b/source/support.tex
@@ -5699,6 +5699,10 @@
 If an explicit specialization or partial specialization of \tcode{type_order} is declared,
 the program is ill-formed.
 
+\pnum
+The templates \tcode{type_order} and \tcode{type_order_v}
+may be instantiated with incomplete types as arguments.
+
 \pnum
 \recommended
 The order should be lexicographical on parameter-type-lists and template argument lists.