diff --git a/stl/inc/chrono b/stl/inc/chrono
index ef8d383e0a..0035ee7102 100644
--- a/stl/inc/chrono
+++ b/stl/inc/chrono
@@ -5469,9 +5469,14 @@ namespace chrono {
     void _Write_seconds(basic_ostream<_CharT, _Traits>& _Os, const hh_mm_ss<_Duration>& _Val) {
         _Os << _STD format(_STATICALLY_WIDEN(_CharT, "{:02}"), _Val.seconds().count());
         if constexpr (hh_mm_ss<_Duration>::fractional_width > 0) {
-            _Os << _STD format(_STATICALLY_WIDEN(_CharT, "{0}{1:0{2}}"),
-                _STD use_facet<numpunct<_CharT>>(_Os.getloc()).decimal_point(), _Val.subseconds().count(),
-                _Val.fractional_width);
+            _Os << _STD use_facet<numpunct<_CharT>>(_Os.getloc()).decimal_point();
+            if constexpr (treat_as_floating_point_v<typename hh_mm_ss<_Duration>::precision::rep>) {
+                _Os << _STD format(_STATICALLY_WIDEN(_CharT, "{:0{}.0f}"), _STD floor(_Val.subseconds().count()),
+                    _Val.fractional_width);
+            } else {
+                _Os << _STD format(
+                    _STATICALLY_WIDEN(_CharT, "{:0{}}"), _Val.subseconds().count(), _Val.fractional_width);
+            }
         }
     }
 
diff --git a/tests/std/tests/P0355R7_calendars_and_time_zones_formatting/test.cpp b/tests/std/tests/P0355R7_calendars_and_time_zones_formatting/test.cpp
index 0305df6786..4cdaac2844 100644
--- a/tests/std/tests/P0355R7_calendars_and_time_zones_formatting/test.cpp
+++ b/tests/std/tests/P0355R7_calendars_and_time_zones_formatting/test.cpp
@@ -593,6 +593,14 @@ void test_hh_mm_ss_formatter() {
     empty_braces_helper(hh_mm_ss{4083007ms}, STR("01:08:03.007"));
     empty_braces_helper(hh_mm_ss{65745123ms}, STR("18:15:45.123"));
     empty_braces_helper(hh_mm_ss{65745s}, STR("18:15:45"));
+    empty_braces_helper(hh_mm_ss{0.1ns}, STR("00:00:00.000000000"));
+    empty_braces_helper(hh_mm_ss{1.45ns}, STR("00:00:00.000000001"));
+    empty_braces_helper(hh_mm_ss{1.56ns}, STR("00:00:00.000000001"));
+    empty_braces_helper(hh_mm_ss{1e+8ns}, STR("00:00:00.100000000"));
+    empty_braces_helper(hh_mm_ss{999'999.9us}, STR("00:00:00.999999"));
+    empty_braces_helper(hh_mm_ss{59'999'999.9us}, STR("00:00:59.999999"));
+    empty_braces_helper(hh_mm_ss{3'599'999'999.9us}, STR("00:59:59.999999"));
+    empty_braces_helper(hh_mm_ss{86'399'999'999.9us}, STR("23:59:59.999999"));
 
     assert(format(STR("{:%H %I %M %S %r %R %T %p}"), hh_mm_ss{13h + 14min + 15351ms})
            == STR("13 01 14 15.351 01:14:15 PM 13:14 13:14:15.351 PM"));