diff --git a/index.js b/index.js
index b21f71e..194bff7 100644
--- a/index.js
+++ b/index.js
@@ -63,6 +63,8 @@ function parseTimestring (string, returnUnit, opts) {
 
       totalSeconds += getSeconds(value, unit, unitValues)
     })
+  } else {
+    throw new Error(`The string [${string}] is invalid for timestring`)
   }
 
   if (returnUnit) {