diff --git a/build/php.m4 b/build/php.m4
index c66550114ab..a5b18c15aaf 100644
--- a/build/php.m4
+++ b/build/php.m4
@@ -308,8 +308,8 @@ dnl
 dnl PHP_CHECK_GCC_ARG(arg, action-if-found, action-if-not-found)
 dnl
 AC_DEFUN([PHP_CHECK_GCC_ARG],[
-  gcc_arg_name=[ac_cv_gcc_arg]translit($1,A-Z-,a-z_)
-  AC_CACHE_CHECK([whether $CC supports $1], [ac_cv_gcc_arg]translit($1,A-Z-,a-z_), [
+  gcc_arg_name=[ac_cv_gcc_arg]translit($1,A-Z=-,a-z__)
+  AC_CACHE_CHECK([whether $CC supports $1], [ac_cv_gcc_arg]translit($1,A-Z=-,a-z__), [
   echo 'void somefunc() { };' > conftest.c
   cmd='$CC $1 -c conftest.c'
   if eval $cmd 2>&1 | $EGREP -e $1 >/dev/null ; then