diff --git a/library/hmac_drbg.c b/library/hmac_drbg.c
index baef526..619b446 100644
--- a/library/hmac_drbg.c
+++ b/library/hmac_drbg.c
@@ -29,7 +29,11 @@
  *  References below are based on rev. 1 (January 2012).
  */
 
+#if !defined(POLARSSL_CONFIG_FILE)
 #include "polarssl/config.h"
+#else
+#include POLARSSL_CONFIG_FILE
+#endif
 
 #if defined(POLARSSL_HMAC_DRBG_C)