diff --git a/doc/api.rst b/doc/api.rst
index e4d4f2d0..8e88b6e1 100644
--- a/doc/api.rst
+++ b/doc/api.rst
@@ -97,6 +97,10 @@ string checks, output iterator and user-defined type support.
 Compile-time Format String Checks
 ---------------------------------
 
+Compile-time checks are supported for built-in and string types as well as
+user-defined types with ``constexpr`` ``parse`` functions in their ``formatter``
+specializations.
+
 .. doxygendefine:: FMT_STRING
 
 Formatting User-defined Types