diff --git a/lib/ask.js b/lib/ask.js
index 88650b8aac..00b810e136 100644
--- a/lib/ask.js
+++ b/lib/ask.js
@@ -34,6 +34,8 @@ module.exports = function ask (prompts, data, done) {
 function prompt (data, key, prompt, done) {
   // skip prompts whose when condition is not met
   if (prompt.when && !evaluate(prompt.when, data)) {
+    // set undefined value to avoid failure on filter evaluations
+    data[key] = undefined
     return done()
   }