diff --git a/include/proxy/proxy.h b/include/proxy/proxy.h
index c3697d94..ba0a584a 100644
--- a/include/proxy/proxy.h
+++ b/include/proxy/proxy.h
@@ -48,6 +48,8 @@
 
 namespace pro {
 
+inline namespace v4 {
+
 namespace details {
 
 struct applicable_traits { static constexpr bool applicable = true; };
@@ -2340,6 +2342,8 @@ struct weak_dispatch : D {
       { ___PRO_THROW(not_implemented{}); }
 };
 
+}  // inline namespace v4
+
 }  // namespace pro
 
 #if __STDC_HOSTED__ && __has_include(<format>)
diff --git a/include/proxy/proxy.ixx b/include/proxy/proxy.ixx
index 1779095b..1486e432 100644
--- a/include/proxy/proxy.ixx
+++ b/include/proxy/proxy.ixx
@@ -4,7 +4,7 @@ module;
 
 export module proxy;
 
-export namespace pro {
+export namespace pro::v4 {
 using pro::constraint_level;
 using pro::proxiable_ptr_constraints;
 using pro::facade_aware_overload_t;
diff --git a/include/proxy/proxy_fmt.h b/include/proxy/proxy_fmt.h
index 715a27e3..b78ca7b4 100644
--- a/include/proxy/proxy_fmt.h
+++ b/include/proxy/proxy_fmt.h
@@ -22,6 +22,8 @@ later) are included before proxy_fmt.h.
 
 namespace pro {
 
+inline namespace v4 {
+
 namespace details {
 
 template <class CharT> struct fmt_format_overload_traits;
@@ -64,6 +66,8 @@ using fmt_wformat = typename FB::template add_convention<
 
 }  // namespace skills
 
+}  // inline namespace v4
+
 }  // namespace pro
 
 namespace fmt {