diff --git a/.github/workflows/linux.yml b/.github/workflows/linux.yml
index 70085f5c6778..961c934ffaac 100644
--- a/.github/workflows/linux.yml
+++ b/.github/workflows/linux.yml
@@ -28,6 +28,11 @@ jobs:
             std: 17
             install: sudo apt install g++-8
             os: ubuntu-18.04
+          - cxx: g++-9
+            build_type: Debug
+            std: 17
+            install: sudo apt install g++-9
+            os: ubuntu-18.04
           - cxx: g++-10
             build_type: Debug
             std: 17
diff --git a/include/fmt/chrono.h b/include/fmt/chrono.h
index b112f76e991c..4c702c20e728 100644
--- a/include/fmt/chrono.h
+++ b/include/fmt/chrono.h
@@ -427,7 +427,7 @@ auto write(OutputIt out, const std::tm& time, const std::locale& loc,
            char format, char modifier = 0) -> OutputIt {
   auto&& buf = get_buffer<Char>(out);
   do_write<Char>(buf, time, loc, format, modifier);
-  return buf.out();
+  return get_iterator(buf);
 }
 
 template <typename Char, typename OutputIt,
@@ -1397,7 +1397,7 @@ inline bool isfinite(T) {
 template <typename T, typename Int, FMT_ENABLE_IF(std::is_integral<T>::value)>
 inline Int to_nonnegative_int(T value, Int upper) {
   FMT_ASSERT(std::is_unsigned<Int>::value ||
-             (value >= 0 && to_unsigned(value) <= to_unsigned(upper)),
+                 (value >= 0 && to_unsigned(value) <= to_unsigned(upper)),
              "invalid value");
   (void)upper;
   return static_cast<Int>(value);
diff --git a/include/fmt/xchar.h b/include/fmt/xchar.h
index 40afbb43d8c6..1dc863243f53 100644
--- a/include/fmt/xchar.h
+++ b/include/fmt/xchar.h
@@ -22,10 +22,9 @@ namespace detail {
 template <typename T>
 using is_exotic_char = bool_constant<!std::is_same<T, char>::value>;
 
-template <typename OutputIt>
-auto write_loc(OutputIt out, loc_value value,
-               const basic_format_specs<wchar_t>& specs, locale_ref loc)
-    -> bool {
+inline auto write_loc(std::back_insert_iterator<detail::buffer<wchar_t>> out,
+                      loc_value value, const basic_format_specs<wchar_t>& specs,
+                      locale_ref loc) -> bool {
 #ifndef FMT_STATIC_THOUSANDS_SEPARATOR
   auto& numpunct =
       std::use_facet<std::numpunct<wchar_t>>(loc.get<std::locale>());