diff --git a/action.yml b/action.yml
index 8eae491..69fb974 100644
--- a/action.yml
+++ b/action.yml
@@ -17,7 +17,7 @@ inputs:
     description: An optional user-agent string
     default: actions/github-script
   previews:
-    description: A list of API previews to accept
+    description: A comma-separated list of API previews to accept
 outputs:
   result:
     description: The return value of the script, stringified with `JSON.stringify`
diff --git a/main.js b/main.js
index 21ec07b..1cc8321 100644
--- a/main.js
+++ b/main.js
@@ -11,9 +11,9 @@ async function main() {
   const userAgent = core.getInput('user-agent')
   const previews = core.getInput('previews')
   const opts = {}
-  if (debug) opts.log = console
-  if (userAgent) opts.userAgent = userAgent
-  if (previews) opts.previews = previews
+  if (debug === 'true') opts.log = console
+  if (userAgent != null) opts.userAgent = userAgent
+  if (previews != null) opts.previews = previews.split(',')
   const client = new GitHub(token, opts)
   const script = core.getInput('script', {required: true})
   const fn = new AsyncFunction('github', 'context', script)