diff --git a/core/js/visitortimezone.js b/core/js/visitortimezone.js
index ee0105c783..d9b63a1087 100644
--- a/core/js/visitortimezone.js
+++ b/core/js/visitortimezone.js
@@ -1,4 +1,10 @@
 $(document).ready(function () {
 		var visitortimezone = (-new Date().getTimezoneOffset() / 60);
 		$('#timezone-offset').val(visitortimezone);
+
+		// only enable the submit button once we are sure that the timezone is set
+		var $loginForm = $('form[name="login"]');
+		if ($loginForm.length) {
+			$loginForm.find('input#submit').prop('disabled', false);
+		}
 });
diff --git a/core/templates/login.php b/core/templates/login.php
index 65f760c1ee..669d20b32e 100644
--- a/core/templates/login.php
+++ b/core/templates/login.php
@@ -51,7 +51,7 @@
 		<label for="remember_login"><?php p($l->t('remember')); ?></label>
 		<?php endif; ?>
 		<input type="hidden" name="timezone-offset" id="timezone-offset"/>
-		<input type="submit" id="submit" class="login primary" value="<?php p($l->t('Log in')); ?>"/>
+		<input type="submit" id="submit" class="login primary" value="<?php p($l->t('Log in')); ?>" disabled="disabled"/>
 	</fieldset>
 </form>
 <?php if (!empty($_['alt_login'])) { ?>