diff --git a/ssl/custom_extensions.cc b/ssl/custom_extensions.cc
index f438f73..84463fa 100644
--- a/ssl/custom_extensions.cc
+++ b/ssl/custom_extensions.cc
@@ -12,6 +12,8 @@
  * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
  * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
 
+#define BORINGSSL_INTERNAL_CXX_TYPES
+
 #include <openssl/ssl.h>
 
 #include <assert.h>
@@ -25,6 +27,8 @@
 #include "internal.h"
 
 
+namespace bssl {
+
 void SSL_CUSTOM_EXTENSION_free(SSL_CUSTOM_EXTENSION *custom_extension) {
   OPENSSL_free(custom_extension);
 }
@@ -246,6 +250,10 @@
   return 1;
 }
 
+}  // namespace bssl
+
+using namespace bssl;
+
 int SSL_CTX_add_client_custom_ext(SSL_CTX *ctx, unsigned extension_value,
                                   SSL_custom_ext_add_cb add_cb,
                                   SSL_custom_ext_free_cb free_cb, void *add_arg,