diff --git a/index.js b/index.js
index 69587da..1b7d52b 100644
--- a/index.js
+++ b/index.js
@@ -1642,7 +1642,7 @@ function unpackneg(r, p) {
   return 0;
 }
 
-function crypto_sign_open(msg, sm, pk) {
+function crypto_sign_open(sm, msg, pk) {
   check(msg, sm.length - crypto_sign_BYTES)
   check(sm, crypto_sign_BYTES)
   check(pk, crypto_sign_PUBLICKEYBYTES)