diff --git a/src/test/java/com/github/kokorin/jaffree/util/ParseUtilTest.java b/src/test/java/com/github/kokorin/jaffree/util/ParseUtilTest.java
index b2fc03de..111a89a1 100644
--- a/src/test/java/com/github/kokorin/jaffree/util/ParseUtilTest.java
+++ b/src/test/java/com/github/kokorin/jaffree/util/ParseUtilTest.java
@@ -69,6 +69,9 @@ public void parseKibiByteFormats() {
 
         final Long newFormat = ParseUtil.parseSizeInKibiBytes("2904KiB");
         Assert.assertEquals(2904L, newFormat.longValue());
+
+        final Long unknownFormat = ParseUtil.parseSizeInKibiBytes("2904KB");
+        Assert.assertNull(unknownFormat);
     }
 
     @Test