diff --git a/libstdc++-v3/include/std/format b/libstdc++-v3/include/std/format
index a8db10d6460c089dc4912aa4b3050d8879165411..40c7d6128f6065e88547f5e09bfe16ad160dc8ac 100644
--- a/libstdc++-v3/include/std/format
+++ b/libstdc++-v3/include/std/format
@@ -309,7 +309,7 @@ namespace __format
     // Presentation types for integral types (including bool and charT).
     _Pres_d = 1, _Pres_b, _Pres_B, _Pres_o, _Pres_x, _Pres_X, _Pres_c,
     // Presentation types for floating-point types.
-    _Pres_a = 1, _Pres_A, _Pres_e, _Pres_E, _Pres_f, _Pres_g, _Pres_G,
+    _Pres_a = 1, _Pres_A, _Pres_e, _Pres_E, _Pres_f, _Pres_F, _Pres_g, _Pres_G,
     _Pres_p = 0, _Pres_P,   // For pointers.
     _Pres_s = 0,            // For strings and bool.
     _Pres_esc = 0xf,        // For strings and charT.
@@ -1382,10 +1382,13 @@ namespace __format
 	    ++__first;
 	    break;
 	  case 'f':
-	  case 'F':
 	    __spec._M_type = _Pres_f;
 	    ++__first;
 	    break;
+	  case 'F':
+	    __spec._M_type = _Pres_F;
+	    ++__first;
+	    break;
 	  case 'g':
 	    __spec._M_type = _Pres_g;
 	    ++__first;
@@ -1442,6 +1445,9 @@ namespace __format
 	      __use_prec = true;
 	      __fmt = chars_format::scientific;
 	      break;
+	    case _Pres_F:
+	      __upper = true;
+	      [[fallthrough]];
 	    case _Pres_f:
 	      __use_prec = true;
 	      __fmt = chars_format::fixed;
diff --git a/libstdc++-v3/testsuite/std/format/functions/format.cc b/libstdc++-v3/testsuite/std/format/functions/format.cc
index 4db5202815d6262e83d50ea60818e2a4e7669e44..59ed3be8baa36052ba569d963d9496e0692646da 100644
--- a/libstdc++-v3/testsuite/std/format/functions/format.cc
+++ b/libstdc++-v3/testsuite/std/format/functions/format.cc
@@ -159,6 +159,18 @@ test_alternate_forms()
   VERIFY( s == "1.e+01 1.e+01 1.e+01" );
 }
 
+void
+test_infnan()
+{
+  double inf = std::numeric_limits<double>::infinity();
+  double nan = std::numeric_limits<double>::quiet_NaN();
+  std::string s;
+  s = std::format("{0} {0:e} {0:E} {0:f} {0:F} {0:g} {0:G} {0:a} {0:A}", inf);
+  VERIFY( s == "inf inf INF inf INF inf INF inf INF" );
+  s = std::format("{0} {0:e} {0:E} {0:f} {0:F} {0:g} {0:G} {0:a} {0:A}", nan);
+  VERIFY( s == "nan nan NAN nan NAN nan NAN nan NAN" );
+}
+
 struct euro_punc : std::numpunct<char>
 {
   std::string do_grouping() const override { return "\3\3"; }