diff --git a/include/mbedtls/hmac_drbg.h b/include/mbedtls/hmac_drbg.h
index dd31fc8..f58b1e3 100644
--- a/include/mbedtls/hmac_drbg.h
+++ b/include/mbedtls/hmac_drbg.h
@@ -24,6 +24,12 @@
 #ifndef MBEDTLS_HMAC_DRBG_H
 #define MBEDTLS_HMAC_DRBG_H
 
+#if !defined(MBEDTLS_CONFIG_FILE)
+#include "config.h"
+#else
+#include MBEDTLS_CONFIG_FILE
+#endif
+
 #include "md.h"
 
 #if defined(MBEDTLS_THREADING_C)