diff --git a/performance/performance.install b/performance/performance.install
index 03a2f26..dbf7200 100644
--- a/performance/performance.install
+++ b/performance/performance.install
@@ -134,10 +134,15 @@ function performance_update_2() {
 function performance_update_7001() {
   $int_field = array('type' => 'int', 'not null' => TRUE, 'default' => 0, 'disp-width' => '11');
 
-  db_change_field('performance_summary', 'millisecs_max', 'ms_max', $int_field);
-  db_change_field('performance_summary', 'millisecs_avg', 'ms_avg', $int_field);
-  db_change_field('performance_detail',  'millisecs',     'ms',     $int_field);
-
+  if (db_field_exists('performance_summary', 'millisecs_max')) {
+    db_change_field('performance_summary', 'millisecs_max', 'ms_max', $int_field);
+  }
+  if (db_field_exists('performance_summary', 'millisecs_avg')) {
+    db_change_field('performance_summary', 'millisecs_avg', 'ms_avg', $int_field);
+  }
+  if (db_field_exists('performance_detail', 'millisecs')) {
+    db_change_field('performance_detail', 'millisecs', 'ms', $int_field);
+  }
   // We don't have a cache update method, so it's better to clear it
   if (function_exists('apc_fetch')) {
     apc_clear_cache('user');