diff --git a/include/polarssl/x509_crt.h b/include/polarssl/x509_crt.h
index 8e63381..0081d36 100644
--- a/include/polarssl/x509_crt.h
+++ b/include/polarssl/x509_crt.h
@@ -27,7 +27,11 @@
 #ifndef POLARSSL_X509_CRT_H
 #define POLARSSL_X509_CRT_H
 
+#if !defined(POLARSSL_CONFIG_FILE)
 #include "config.h"
+#else
+#include POLARSSL_CONFIG_FILE
+#endif
 
 #include "x509.h"