diff --git a/tests/test_files.php b/tests/test_files.php
index dcc0c294..3ede3c3d 100644
--- a/tests/test_files.php
+++ b/tests/test_files.php
@@ -77,7 +77,6 @@ $test_files[] = 'HTMLPurifier/ErrorCollectorTest.php';
 $test_files[] = 'HTMLPurifier/EncoderTest.php';
 $test_files[] = 'HTMLPurifier/EntityLookupTest.php';
 $test_files[] = 'HTMLPurifier/EntityParserTest.php';
-$test_files[] = 'HTMLPurifier/Filter/ExtractStyleBlocksTest.php';
 $test_files[] = 'HTMLPurifier/GeneratorTest.php';
 $test_files[] = 'HTMLPurifier/HTMLDefinitionTest.php';
 $test_files[] = 'HTMLPurifier/HTMLModuleManagerTest.php';
@@ -123,6 +122,10 @@ $test_files[] = 'HTMLPurifier/URISchemeTest.php';
 $test_files[] = 'HTMLPurifier/URITest.php';
 $test_files[] = 'HTMLPurifierTest.php';
 
+if ($csstidy_location) {
+  $test_files[] = 'HTMLPurifier/Filter/ExtractStyleBlocksTest.php';
+}
+
 // ConfigDoc auxiliary library
 
 // ... none yet