diff --git a/Classes/PHPExcel/CachedObjectStorageFactory.php b/Classes/PHPExcel/CachedObjectStorageFactory.php
index 45bae0d3..59a97436 100644
--- a/Classes/PHPExcel/CachedObjectStorageFactory.php
+++ b/Classes/PHPExcel/CachedObjectStorageFactory.php
@@ -198,7 +198,7 @@ class PHPExcel_CachedObjectStorageFactory
 
 		self::$_storageMethodParameters[$method] = self::$_storageMethodDefaultParameters[$method];
 		foreach($arguments as $k => $v) {
-			if (isset(self::$_storageMethodParameters[$method][$k])) {
+			if (array_key_exists($k, self::$_storageMethodParameters[$method])) {
 				self::$_storageMethodParameters[$method][$k] = $v;
 			}
 		}
diff --git a/changelog.txt b/changelog.txt
index 7405b8e7..b5d49565 100644
--- a/changelog.txt
+++ b/changelog.txt
@@ -28,6 +28,7 @@ Fixed in develop branch:
 - Bugfix:   (Asker)    Work item 18777 - Error in PHPEXCEL/Calculation.php script on line 2976 (stack pop check)
 - Bugfix:   (MBaker)   Work item 18794 - CSV files without a file extension being identified as HTML
 - Bugfix:   (AndreKR)  Work item GH-66 - Wrong check for maximum number of rows in Excel5 Writer
+- Bugfix:   (MBaker)   Work item GH-67 - Cache directory for DiscISAM cache storage cannot be set
 - General:  (kea)      Work item GH-69 - Improved AdvancedValueBinder for currency
 - General:  (MBaker)   Work items 17936 and 17840 - Fix for environments where there is no access to /tmp but to upload_tmp_dir
                        Provided an option to set the sys_get_temp_dir() call to use the upload_tmp_dir; though by default the standard temp directory will still be used