diff --git a/index.js b/index.js
index 793755c..e2bc9ba 100644
--- a/index.js
+++ b/index.js
@@ -63,5 +63,6 @@ function parse(str, format){
     units = parse[units] || parse[units.toLowerCase().replace(/s$/, '')]
     if (units) result = (result || 0) + parseFloat(n, 10) * units
   })
-  return result / parse[format]
+
+  return result && (result / parse[format])
 }
diff --git a/test.js b/test.js
index b12571a..c32a185 100644
--- a/test.js
+++ b/test.js
@@ -114,3 +114,9 @@ t('invalid', t => {
 
 	t.end()
 })
+
+t('format', t => {
+	t.equal(parse('1hr 20mins', 'm'), parse('1hr 20mins') / 1000 / 60)
+
+	t.end()
+})