diff --git a/include/cpp2util.h b/include/cpp2util.h
index 46c6b0fc4..9656099bd 100644
--- a/include/cpp2util.h
+++ b/include/cpp2util.h
@@ -1114,7 +1114,7 @@ inline auto to_string(...) -> std::string {
     return "(customize me - no cpp2::to_string overload exists for this type)";
 }
 
-inline auto to_string(std::any const&) -> std::string {
+inline auto to_string(std::same_as<std::any> auto const&) -> std::string {
     return "std::any";
 }
 
diff --git a/regression-tests/test-results/clang-12/mixed-string-interpolation.cpp.execution b/regression-tests/test-results/clang-12/mixed-string-interpolation.cpp.execution
index 39a058ceb..eebb290a9 100644
--- a/regression-tests/test-results/clang-12/mixed-string-interpolation.cpp.execution
+++ b/regression-tests/test-results/clang-12/mixed-string-interpolation.cpp.execution
@@ -14,4 +14,4 @@ p = (first, (empty))
 t = (3.140000, (empty), (empty))
 vv = 0
 vv = (1, 2.300000)
-custom = std::any
+custom = (customize me - no cpp2::to_string overload exists for this type)