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
diff --git a/library/cipher.c b/library/cipher.c
index cf82a82..fe34929 100644
--- a/library/cipher.c
+++ b/library/cipher.c
@@ -45,10 +45,6 @@
 #include "mbedtls/ccm.h"
 #endif
 
-#if defined(MBEDTLS_ARC4_C) || defined(MBEDTLS_CIPHER_NULL_CIPHER)
-#define MBEDTLS_CIPHER_MODE_STREAM
-#endif
-
 /* Implementation that should never be optimized out by the compiler */
 static void mbedtls_zeroize( void *v, size_t n ) {
     volatile unsigned char *p = v; while( n-- ) *p++ = 0;