diff --git a/gcc/cp/name-lookup.c b/gcc/cp/name-lookup.c
index 092fa6b8768..28271ba0485 100644
--- a/gcc/cp/name-lookup.c
+++ b/gcc/cp/name-lookup.c
@@ -6963,6 +6963,8 @@ get_cxx_dialect_name (enum cxx_dialect dialect)
       return "C++17";
     case cxx20:
       return "C++20";
+    case cxx23:
+      return "C++23";
     }
 }
 
diff --git a/gcc/testsuite/g++.dg/modules/modules.exp b/gcc/testsuite/g++.dg/modules/modules.exp
index 38654caf7b9..da7afc2a226 100644
--- a/gcc/testsuite/g++.dg/modules/modules.exp
+++ b/gcc/testsuite/g++.dg/modules/modules.exp
@@ -35,7 +35,7 @@ if ![info exists DEFAULT_CXXFLAGS] then {
     set DEFAULT_CXXFLAGS " -pedantic-errors -Wno-long-long"
 }
 set DEFAULT_MODFLAGS $DEFAULT_CXXFLAGS
-set MOD_STD_LIST { 17 2a }
+set MOD_STD_LIST { 17 2a 2b }
 
 dg-init