diff --git a/browser-index.js b/browser-index.js
index b6b8541a2..71b81f3ae 100644
--- a/browser-index.js
+++ b/browser-index.js
@@ -1,13 +1,16 @@
 var matrixcs = require("./lib/matrix");
 matrixcs.request(require("browser-request"));
 
-matrixcs.setCryptoStoreFactory(
-    function() {
-        return new matrixcs.IndexedDBCryptoStore(
-            global.indexedDB, "matrix-js-sdk:crypto"
-        );
-    }
-);
+// if our browser (appears to) support indexeddb, use an indexeddb crypto store.
+if (global.indexedDB) {
+    matrixcs.setCryptoStoreFactory(
+        function() {
+            return new matrixcs.IndexedDBCryptoStore(
+                global.indexedDB, "matrix-js-sdk:crypto"
+            );
+        }
+    );
+}
 
 module.exports = matrixcs; // keep export for browserify package deps
 global.matrixcs = matrixcs;