diff --git a/doc/api.rst b/doc/api.rst
index a5532d3a..90634d0f 100644
--- a/doc/api.rst
+++ b/doc/api.rst
@@ -309,7 +309,7 @@ The following user-defined literals are defined in ``fmt/format.h``.
 
 .. doxygenfunction:: operator""_format(const char *s, size_t n) -> detail::udl_formatter<char> 
 
-.. doxygenfunction:: operator""_a() -> detail::udl_arg
+.. doxygenfunction:: operator""_a()
 
 Utilities
 ---------