diff --git a/CHANGELOG.md b/CHANGELOG.md
index 48505f8..5954cce 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -99,6 +99,7 @@ Other changes
 
 | Version        | Date           | Comment  |
 | -------------- | -------------- | -------- |
+| 3.33.7         | 2017-11-28     | bugfix diskLayout().size |
 | 3.33.6         | 2017-11-16     | bugfix diskLayout().size |
 | 3.33.5         | 2017-11-09     | code cleanup |
 | 3.33.4         | 2017-11-09     | bugfix graphics controller win (bytes) |
diff --git a/lib/filesystem.js b/lib/filesystem.js
index a1c2653..4ffeda7 100644
--- a/lib/filesystem.js
+++ b/lib/filesystem.js
@@ -584,8 +584,8 @@ function diskLayout(callback) {
               }
 
               const sizeString = util.getValue(lines, 'size', ':', true).trim();
-              const sizeValue = sizeString.match(/\(([^)]+)\)/)[1];
               if (sizeString && lines.length > 0 && lines[0].trim() === 'disk') {
+                const sizeValue = sizeString.match(/\(([^)]+)\)/)[1];
                 result.push({
                   type: (mediumType === '0' ? 'SSD' : (mediumType === '1' ? 'HD' : (device.indexOf('SSD') > -1 ? 'SSD' : 'HD'))), // to be tested ... /sys/block/sda/queue/rotational
                   name: util.getValue(lines, 'product:', ':', true),