diff --git a/src/isomorphic-btoa.js b/src/isomorphic-btoa.js
index <HASH>..<HASH> 100644
--- a/src/isomorphic-btoa.js
+++ b/src/isomorphic-btoa.js
@@ -1,6 +1,12 @@
 /* global global, require, Buffer */
 
-const globalNamespace = global || window;
+let globalNamespace;
+
+if (typeof global === 'undefined') {
+  globalNamespace = window;
+} else {
+  globalNamespace = global;
+}
 
 const btoa = globalNamespace.btoa;
 
diff --git a/src/isomorphic-fetch.js b/src/isomorphic-fetch.js
index <HASH>..<HASH> 100644
--- a/src/isomorphic-fetch.js
+++ b/src/isomorphic-fetch.js
@@ -1,6 +1,12 @@
 /* global global, require */
 
-const globalNamespace = global || window;
+let globalNamespace;
+
+if (typeof global === 'undefined') {
+  globalNamespace = window;
+} else {
+  globalNamespace = global;
+}
 
 const fetch = globalNamespace.fetch;
If global is undefined, in strict mode, this throws.

Fix by checking types of names, then setting the var.