diff --git a/include/mbedtls/cipher_internal.h b/include/mbedtls/cipher_internal.h
index 969ff9c..2a7fd9a 100644
--- a/include/mbedtls/cipher_internal.h
+++ b/include/mbedtls/cipher_internal.h
@@ -34,6 +34,10 @@
 
 #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 7369f48..0d84ccf 100644
--- a/library/cipher.c
+++ b/library/cipher.c
@@ -56,10 +56,6 @@
 #define mbedtls_free   free
 #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 = (unsigned char*)v; while( n-- ) *p++ = 0;