diff --git a/lib/hash-gen.js b/lib/hash-gen.js
index e3b7cc0..8ba3cff 100755
--- a/lib/hash-gen.js
+++ b/lib/hash-gen.js
@@ -8,7 +8,7 @@ const path = require('path')
 async function run () {
   let [rootPaths, writeLocation, includeDotFiles, ignorePatterns] = process.argv.slice(2)
 
-  if (!rootPaths) {
+  if (rootPaths === undefined || writeLocation === undefined) {
     console.error('Usage: hash <root-path> <write-location> <include-dot-files> <ignore-patterns>')
     process.exit(1)
   }