diff --git a/include/mbedtls/cipher_internal.h b/include/mbedtls/cipher_internal.h
index 6c58bcc..88baa82 100644
--- a/include/mbedtls/cipher_internal.h
+++ b/include/mbedtls/cipher_internal.h
@@ -33,6 +33,10 @@
 
 #include "cipher.h"
 
+#if defined(MBEDTLS_ARC4_C) || defined(MBEDTLS_CIPHER_NULL_CIPHER)
+#define MBEDTLS_CIPHER_MODE_STREAM
+#endif
+
 #ifdef __cplusplus
 extern "C" {
 #endif