diff --git a/include/mbedtls/asn1write.h b/include/mbedtls/asn1write.h
index 76c1780..360540a 100644
--- a/include/mbedtls/asn1write.h
+++ b/include/mbedtls/asn1write.h
@@ -24,6 +24,12 @@
 #ifndef MBEDTLS_ASN1_WRITE_H
 #define MBEDTLS_ASN1_WRITE_H
 
+#if !defined(MBEDTLS_CONFIG_FILE)
+#include "config.h"
+#else
+#include MBEDTLS_CONFIG_FILE
+#endif
+
 #include "asn1.h"
 
 #define MBEDTLS_ASN1_CHK_ADD(g, f)                      \