diff --git a/src/net/addr/ip.cpp b/src/net/addr/ip.cpp
index 96b78cd..a17e4fd 100644
--- a/src/net/addr/ip.cpp
+++ b/src/net/addr/ip.cpp
@@ -7,4 +7,5 @@
 template In6Addr FromStr<In6Addr>::operator()(std::string_view) const;
 template char* ToStr<In6Addr>::operator()(char*, In6Addr) const noexcept;
 template InAnyAddr FromStr<InAnyAddr>::operator()(std::string_view) const;
+template char* ToStr<InAnyAddr>::operator()(char*, InAnyAddr) const noexcept;
 } // namespace stdplus