diff --git a/lib/storageUtil.js b/lib/storageUtil.js
index 3eee94458..bf9573999 100644
--- a/lib/storageUtil.js
+++ b/lib/storageUtil.js
@@ -22,11 +22,8 @@ var storageUtil = {};
 // https://connect.microsoft.com/IE/Feedback/Details/1496040
 storageUtil.browserHasLocalStorage = function() {
   try {
-    if (storageUtil.getLocalStorage()) {
-      return true;
-    } else {
-      return false;
-    }
+    var storage = storageUtil.getLocalStorage();
+    return storageUtil.testStorage(storage);
   } catch (e) {
     return false;
   }
@@ -34,11 +31,8 @@ storageUtil.browserHasLocalStorage = function() {
 
 storageUtil.browserHasSessionStorage = function() {
   try {
-    if (storageUtil.getSessionStorage()) {
-      return true;
-    } else {
-      return false;
-    }
+    var storage = storageUtil.getSessionStorage();
+    return storageUtil.testStorage(storage);
   } catch (e) {
     return false;
   }
@@ -73,4 +67,15 @@ storageUtil.getCookieStorage = function() {
   };
 };
 
+storageUtil.testStorage = function(storage) {
+  var key = 'okta-test-storage';
+  try {
+    storage.setItem(key, key);
+    storage.removeItem(key);
+    return true;
+  } catch (e) {
+    return false;
+  }
+};
+
 module.exports = storageUtil;
diff --git a/test/spec/tokenManager.js b/test/spec/tokenManager.js
index dbf336f1a..7413d33f4 100644
--- a/test/spec/tokenManager.js
+++ b/test/spec/tokenManager.js
@@ -44,6 +44,19 @@ describe('TokenManager', function() {
         'test-idToken': tokens.standardIdTokenParsed
       });
     });
+    it('defaults to sessionStorage if localStorage cannot be written to', function() {
+      jest.spyOn(window.console, 'log');
+      oauthUtil.mockStorageSetItemError();
+      var client = setupSync();
+      expect(window.console.log).toHaveBeenCalledWith(
+        '[okta-auth-sdk] WARN: This browser doesn\'t ' +
+        'support localStorage. Switching to sessionStorage.'
+      );
+      client.tokenManager.add('test-idToken', tokens.standardIdTokenParsed);
+      oauthUtil.expectTokenStorageToEqual(sessionStorage, {
+        'test-idToken': tokens.standardIdTokenParsed
+      });
+    });
     it('defaults to cookie-based storage if localStorage and sessionStorage are not available', function() {
       jest.spyOn(window.console, 'log');
       oauthUtil.mockLocalStorageError();
@@ -61,6 +74,27 @@ describe('TokenManager', function() {
         '2038-01-19T03:14:07.000Z'
       );
     });
+    it('defaults to cookie-based storage if sessionStorage cannot be written to', function() {
+      jest.spyOn(window.console, 'log');
+      oauthUtil.mockLocalStorageError();
+      oauthUtil.mockStorageSetItemError();
+      var client = setupSync({
+        tokenManager: {
+          storage: 'sessionStorage'
+        }
+      });
+      expect(window.console.log).toHaveBeenCalledWith(
+        '[okta-auth-sdk] WARN: This browser doesn\'t ' +
+        'support sessionStorage. Switching to cookie-based storage.'
+      );
+      var setCookieMock = util.mockSetCookie();
+      client.tokenManager.add('test-idToken', tokens.standardIdTokenParsed);
+      expect(setCookieMock).toHaveBeenCalledWith(
+        'okta-token-storage',
+        JSON.stringify({'test-idToken': tokens.standardIdTokenParsed}),
+        '2038-01-19T03:14:07.000Z'
+      );
+    });
   });
 
   describe('add', function() {
diff --git a/test/util/oauthUtil.js b/test/util/oauthUtil.js
index 6deae95d3..72c6392c1 100644
--- a/test/util/oauthUtil.js
+++ b/test/util/oauthUtil.js
@@ -29,6 +29,12 @@ oauthUtil.mockLocalStorageError = function() {
   });
 };
 
+oauthUtil.mockStorageSetItemError = function() {
+  jest.spyOn(Storage.prototype, 'setItem').mockImplementationOnce(function() {
+    throw 'This function is not supported on this system.';
+  });
+};
+
 oauthUtil.mockSessionStorageError = function() {
   jest.spyOn(storageUtil, 'getSessionStorage').mockImplementation(function() {
     throw 'This function is not supported on this system.';