diff --git a/src/format.cc b/src/format.cc
index 22fda622..e75e1724 100644
--- a/src/format.cc
+++ b/src/format.cc
@@ -55,6 +55,7 @@ vformat_to(buffer<char>&, string_view,
                type_identity_t<char>>>);
 }  // namespace detail
 
+// Clang doesn't allow dllexport on template instantiation definitions (LLVM D61118)
 template struct detail::basic_data<void>;
 
 // Workaround a bug in MSVC2013 that prevents instantiation of format_float.