diff --git a/spec/utils-spec.js b/spec/utils-spec.js
index 3b2b73b..0992767 100644
--- a/spec/utils-spec.js
+++ b/spec/utils-spec.js
@@ -90,6 +90,8 @@ describe('gridstack utils', function() {
             expect(utils.parseHeight('12.3vh')).toEqual(jasmine.objectContaining({height: 12.3, unit: 'vh'}));
             expect(utils.parseHeight('12.3vw')).toEqual(jasmine.objectContaining({height: 12.3, unit: 'vw'}));
             expect(utils.parseHeight('12.5')).toEqual(jasmine.objectContaining({height: 12.5, unit: 'px'}));
+            expect(function() { utils.parseHeight('12.5 df'); }).toThrowError('Invalid height');
+
         });
 
         it('should parse negative height value', function() {