diff --git a/libstdc++-v3/include/std/format b/libstdc++-v3/include/std/format
index 01a53143d1c..2e9319cdda6 100644
--- a/libstdc++-v3/include/std/format
+++ b/libstdc++-v3/include/std/format
@@ -1838,9 +1838,9 @@ namespace __format
 
 	  if (_M_spec._M_localized && __builtin_isfinite(__v))
 	    {
-	      __wstr = _M_localize(__str, __expc, __fc.locale());
-	      if (!__wstr.empty())
-		__str = __wstr;
+	      auto __s = _M_localize(__str, __expc, __fc.locale());
+	      if (!__s.empty())
+		__str = __wstr = std::move(__s);
 	    }
 
 	  size_t __width = _M_spec._M_get_width(__fc);
diff --git a/libstdc++-v3/testsuite/std/format/functions/format.cc b/libstdc++-v3/testsuite/std/format/functions/format.cc
index 000f2671816..93c33b456e6 100644
--- a/libstdc++-v3/testsuite/std/format/functions/format.cc
+++ b/libstdc++-v3/testsuite/std/format/functions/format.cc
@@ -370,6 +370,18 @@ test_wchar()
   // P2909R4 Fix formatting of code units as integers (Dude, where’s my char?)
   s = std::format(L"{:d} {:d}", wchar_t(-1), char(-1));
   VERIFY( s.find('-') == std::wstring::npos );
+
+  auto ws = std::format(L"{:L}", 0.5);
+  VERIFY( ws == L"0.5" );
+  // The default C locale.
+  std::locale cloc = std::locale::classic();
+  // PR libstdc++/119671 use-after-free formatting floating-point to wstring
+  ws = std::format(cloc, L"{:L}", 0.5);
+  VERIFY( ws == L"0.5" );
+  // A locale with no name, but with the same facets as the C locale.
+  std::locale locx(cloc, &std::use_facet<std::ctype<char>>(cloc));
+  ws = std::format(locx, L"{:L}", 0.5);
+  VERIFY( ws == L"0.5" );
 }
 
 void