diff --git a/sea.js b/sea.js
index 92a0a0c69..c0cd5860a 100644
--- a/sea.js
+++ b/sea.js
@@ -51,7 +51,7 @@
     if(typeof Buffer === "undefined") {
       root.Buffer = require("buffer").Buffer
     }
-    if(typeof btoa !== "undefined"){
+    if(typeof btoa === "undefined"){
       root.btoa = function (data) { return Buffer.from(data, "binary").toString("base64"); };
       root.atob = function (data) { return Buffer.from(data, "base64").toString("binary"); };
     }
diff --git a/sea/base64.js b/sea/base64.js
index 48b78725e..3eff26823 100644
--- a/sea/base64.js
+++ b/sea/base64.js
@@ -2,7 +2,7 @@
     if(typeof Buffer === "undefined") {
       root.Buffer = require("buffer").Buffer
     }
-    if(typeof btoa !== "undefined"){
+    if(typeof btoa === "undefined"){
       root.btoa = function (data) { return Buffer.from(data, "binary").toString("base64"); };
       root.atob = function (data) { return Buffer.from(data, "base64").toString("binary"); };
     }