diff --git a/modules/filter/filter.module b/modules/filter/filter.module
index 7b451b7..d77735d 100644
--- a/modules/filter/filter.module
+++ b/modules/filter/filter.module
@@ -748,7 +748,7 @@ function check_markup($text, $format_id = NULL, $langcode = '', $cache = FALSE)
 
   // Give filters the chance to escape HTML-like data such as code or formulas.
   foreach ($filters as $name => $filter) {
-    if ($filter->status && isset($filter_info[$name]['prepare callback']) && function_exists($filter_info[$name]['prepare callback'])) {
+    if ($filter->status && isset($filter_info[$name]['prepare callback'])) {
       $function = $filter_info[$name]['prepare callback'];
       $text = $function($text, $filter, $format, $langcode, $cache, $cache_id);
     }
@@ -756,7 +756,7 @@ function check_markup($text, $format_id = NULL, $langcode = '', $cache = FALSE)
 
   // Perform filtering.
   foreach ($filters as $name => $filter) {
-    if ($filter->status && isset($filter_info[$name]['process callback']) && function_exists($filter_info[$name]['process callback'])) {
+    if ($filter->status && isset($filter_info[$name]['process callback'])) {
       $function = $filter_info[$name]['process callback'];
       $text = $function($text, $filter, $format, $langcode, $cache, $cache_id);
     }