diff --git a/application/tests/_ci_phpunit_test/CIPHPUnitTest.php b/application/tests/_ci_phpunit_test/CIPHPUnitTest.php
index <HASH>..<HASH> 100644
--- a/application/tests/_ci_phpunit_test/CIPHPUnitTest.php
+++ b/application/tests/_ci_phpunit_test/CIPHPUnitTest.php
@@ -57,7 +57,13 @@ class CIPHPUnitTest
 			require_once BASEPATH . 'core/CodeIgniter.php';
 		} catch (CIPHPUnitTestShow404Exception $e) {
 			// Catch 404 exception
-			ob_end_clean();
+			// if statement below is needed. If there is not, following error
+			// ocurrs when you use `@runInSeparateProcess`
+			// ob_end_clean(): failed to delete buffer. No buffer to deleteF
+			if (ob_get_length() > 0 )
+			{
+				ob_end_clean();
+			}
 			new CI_Controller();
 		}
Fix bug that "ob_end_clean(): failed to delete buffer" error occurs when you use @runInSeparateProcess