diff --git a/configure b/configure
index 99a162629f..052113bcea 100755
--- a/configure
+++ b/configure
@@ -8071,8 +8071,8 @@ test-config-cflags-finput-charset-ascii = $libc_cv_test_cflags_finput_charset_as
 
 saved_CXX="$CXX"
 CXX="$TEST_CXX"
-{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking -finput-charset=ascii in testing" >&5
-printf %s "checking -finput-charset=ascii in testing... " >&6; }
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking $CXX -finput-charset=ascii in testing" >&5
+printf %s "checking $CXX -finput-charset=ascii in testing... " >&6; }
 if test ${libc_cv_test_cxxflags_finput_charset_ascii+y}
 then :
   printf %s "(cached) " >&6
diff --git a/configure.ac b/configure.ac
index a535a09de8..fc5ddb8561 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1610,7 +1610,7 @@ LIBC_CONFIG_VAR(test-config-cflags-finput-charset-ascii,
 		$libc_cv_test_cflags_finput_charset_ascii)
 
 dnl Check if TEST_CXX supports -finput-charset=ascii.
-LIBC_TRY_TEST_CXX_OPTION([-finput-charset=ascii],
+LIBC_TRY_TEST_CXX_OPTION([$CXX -finput-charset=ascii],
   [-c -Werror -finput-charset=ascii],
   libc_cv_test_cxxflags_finput_charset_ascii,
   [libc_cv_test_cxxflags_finput_charset_ascii="-finput-charset=ascii"],