diff --git a/include/mbedtls/pem.h b/include/mbedtls/pem.h
index 2cf4c0a..8191850 100644
--- a/include/mbedtls/pem.h
+++ b/include/mbedtls/pem.h
@@ -24,6 +24,12 @@
 #ifndef MBEDTLS_PEM_H
 #define MBEDTLS_PEM_H
 
+#if !defined(MBEDTLS_CONFIG_FILE)
+#include "config.h"
+#else
+#include MBEDTLS_CONFIG_FILE
+#endif
+
 #include <stddef.h>
 
 /**