diff --git a/system/libraries/Unit_test.php b/system/libraries/Unit_test.php
index b2f4bf8..d3e1513 100644
--- a/system/libraries/Unit_test.php
+++ b/system/libraries/Unit_test.php
@@ -57,8 +57,8 @@
 		if ($this->active == FALSE)
 			return;
 			
-		if (in_array($expected, array('is_string', 'is_bool', 'is_true', 'is_false', 'is_int', 'is_numeric', 'is_float', 'is_double', 'is_array', 'is_null')))
-		{		
+		if ($expected !== 0 AND in_array($expected, array('is_string', 'is_bool', 'is_true', 'is_false', 'is_int', 'is_numeric', 'is_float', 'is_double', 'is_array', 'is_null')))
+		{
 			$expected = str_replace('is_float', 'is_double', $expected);
 			$result = ($expected($test)) ? TRUE : FALSE;	
 			$extype = str_replace(array('true', 'false'), 'bool', str_replace('is_', '', $expected));