diff --git a/include/mbedtls/ctr_drbg.h b/include/mbedtls/ctr_drbg.h
index 10f9389..838f5f1 100644
--- a/include/mbedtls/ctr_drbg.h
+++ b/include/mbedtls/ctr_drbg.h
@@ -36,6 +36,12 @@
 #ifndef MBEDTLS_CTR_DRBG_H
 #define MBEDTLS_CTR_DRBG_H
 
+#if !defined(MBEDTLS_CONFIG_FILE)
+#include "config.h"
+#else
+#include MBEDTLS_CONFIG_FILE
+#endif
+
 #include "aes.h"
 
 #if defined(MBEDTLS_THREADING_C)