diff --git a/library/pem.c b/library/pem.c
index 1cc23ba..2f639d0 100644
--- a/library/pem.c
+++ b/library/pem.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_PEM_PARSE_C) || defined(POLARSSL_PEM_WRITE_C)
 #include "polarssl/pem.h"