diff --git a/library/bignum.c b/library/bignum.c
index 5fbb7d3..ac7f25c 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -30,7 +30,11 @@
  *  http://math.libtomcrypt.com/files/tommath.pdf
  */
 
+#if !defined(POLARSSL_CONFIG_FILE)
 #include "polarssl/config.h"
+#else
+#include POLARSSL_CONFIG_FILE
+#endif
 
 #if defined(POLARSSL_BIGNUM_C)