diff --git a/gcc/testsuite/g++.dg/cpp/warning-1.C b/gcc/testsuite/g++.dg/cpp/warning-1.C
new file mode 100644
index 0000000000000000000000000000000000000000..2d857cf747c9012889172af6a3b8110a186c9dec
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp/warning-1.C
@@ -0,0 +1,6 @@
+// P2437R1 - Support for #warning
+// { dg-do preprocess }
+// { dg-options "-pedantic-errors" }
+
+#warning example text /* { dg-warning "example text" } */
+// { dg-error "#warning before C\\\+\\\+23 is a GCC extension" "pedantic" { target c++20_down } .-1 }
diff --git a/gcc/testsuite/g++.dg/cpp/warning-2.C b/gcc/testsuite/g++.dg/cpp/warning-2.C
new file mode 100644
index 0000000000000000000000000000000000000000..d6d5d9fc0813061f1837ad59ce1d7790dfc8e67a
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp/warning-2.C
@@ -0,0 +1,6 @@
+// P2437R1 - Support for #warning
+// { dg-do preprocess }
+// { dg-options "-pedantic" }
+
+#warning example text /* { dg-warning "example text" } */
+// { dg-warning "#warning before C\\\+\\\+23 is a GCC extension" "pedantic" { target c++20_down } .-1 }
diff --git a/gcc/testsuite/g++.dg/cpp/warning-3.C b/gcc/testsuite/g++.dg/cpp/warning-3.C
new file mode 100644
index 0000000000000000000000000000000000000000..1595b4d13053905c1d55590dd80c674472d8e9ad
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp/warning-3.C
@@ -0,0 +1,6 @@
+// P2437R1 - Support for #warning
+// { dg-do preprocess }
+// { dg-options "" }
+
+#warning example text /* { dg-warning "example text" } */
+// { dg-bogus "#warning before C\\\+\\\+23 is a GCC extension" "" { target *-*-* } .-1 }
diff --git a/libcpp/directives.cc b/libcpp/directives.cc
index 802bd8c8bb5c6a2521cd78b87275f20f236a7173..918752f6b1f0f51a24df6ed246d01f90c6187880 100644
--- a/libcpp/directives.cc
+++ b/libcpp/directives.cc
@@ -388,8 +388,14 @@ directive_diagnostics (cpp_reader *pfile, const directive *dir, int indented)
       else if (dir == &dtable[T_WARNING])
 	{
 	  if (CPP_PEDANTIC (pfile) && !CPP_OPTION (pfile, warning_directive))
-	    cpp_error (pfile, CPP_DL_PEDWARN,
-		       "#%s before C2X is a GCC extension", dir->name);
+	    {
+	      if (CPP_OPTION (pfile, cplusplus))
+		cpp_error (pfile, CPP_DL_PEDWARN,
+			   "#%s before C++23 is a GCC extension", dir->name);
+	      else
+		cpp_error (pfile, CPP_DL_PEDWARN,
+			   "#%s before C2X is a GCC extension", dir->name);
+	    }
 	  else if (CPP_OPTION (pfile, cpp_warn_c11_c2x_compat) > 0)
 	    cpp_warning (pfile, CPP_W_C11_C2X_COMPAT,
 			 "#%s before C2X is a GCC extension", dir->name);
diff --git a/libcpp/init.cc b/libcpp/init.cc
index b184e1ffd995176eb2c7f00c3761ed56e653712f..39e7e75f010dcb687e76adc8ab99dfef9e14632e 100644
--- a/libcpp/init.cc
+++ b/libcpp/init.cc
@@ -123,8 +123,8 @@ static const struct lang_flags lang_defaults[] =
   /* CXX17    */  { 1,  1,  1,  1,  1,  1,  1,   1,   1,   1,    1,     1,     0,   1,      0,   1,     0,   0,   0,      0,      0 },
   /* GNUCXX20 */  { 1,  1,  1,  1,  1,  0,  1,   1,   1,   1,    1,     1,     0,   1,      1,   1,     0,   0,   0,      0,      0 },
   /* CXX20    */  { 1,  1,  1,  1,  1,  1,  1,   1,   1,   1,    1,     1,     0,   1,      1,   1,     0,   0,   0,      0,      0 },
-  /* GNUCXX23 */  { 1,  1,  1,  1,  1,  0,  1,   1,   1,   1,    1,     1,     0,   1,      1,   1,     0,   1,   1,      0,      1 },
-  /* CXX23    */  { 1,  1,  1,  1,  1,  1,  1,   1,   1,   1,    1,     1,     0,   1,      1,   1,     0,   1,   1,      0,      1 },
+  /* GNUCXX23 */  { 1,  1,  1,  1,  1,  0,  1,   1,   1,   1,    1,     1,     0,   1,      1,   1,     0,   1,   1,      1,      1 },
+  /* CXX23    */  { 1,  1,  1,  1,  1,  1,  1,   1,   1,   1,    1,     1,     0,   1,      1,   1,     0,   1,   1,      1,      1 },
   /* ASM      */  { 0,  0,  1,  0,  0,  0,  0,   0,   0,   0,    0,     0,     0,   0,      0,   0,     0,   0,   0,      0,      0 }
 };