diff --git a/c_src/enacl_nif.c b/c_src/enacl_nif.c
index ccc6ebe..ed4f310 100644
--- a/c_src/enacl_nif.c
+++ b/c_src/enacl_nif.c
@@ -5,6 +5,7 @@
 
 #include "enacl.h"
 #include "generichash.h"
+#include "hash.h"
 
 #define CRYPTO_SIGN_STATE_RESOURCE "crypto_sign_state"