diff --git a/library/asn1write.c b/library/asn1write.c
index 626e0ff..314c9f9 100644
--- a/library/asn1write.c
+++ b/library/asn1write.c
@@ -23,7 +23,11 @@
  *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
+#if !defined(POLARSSL_CONFIG_FILE)
 #include "polarssl/config.h"
+#else
+#include POLARSSL_CONFIG_FILE
+#endif
 
 #if defined(POLARSSL_ASN1_WRITE_C)