diff --git a/core/modules/simpletest/simpletest.install b/core/modules/simpletest/simpletest.install
index c1422e6..3a57dd4 100644
--- a/core/modules/simpletest/simpletest.install
+++ b/core/modules/simpletest/simpletest.install
@@ -94,10 +94,8 @@ function simpletest_schema() {
         'description' => 'Test ID, messages belonging to the same ID are reported together',
       ),
       'test_class' => array(
-        'type' => 'varchar_ascii',
-        'length' => 255,
+        'type' => 'text',
         'not null' => TRUE,
-        'default' => '',
         'description' => 'The name of the class that created this message.',
       ),
       'status' => array(
@@ -120,10 +118,8 @@ function simpletest_schema() {
         'description' => 'The message group this message belongs to. For example: warning, browser, user.',
       ),
       'function' => array(
-        'type' => 'varchar_ascii',
-        'length' => 255,
+        'type' => 'text',
         'not null' => TRUE,
-        'default' => '',
         'description' => 'Name of the assertion function or method that created this message.',
       ),
       'line' => array(