diff --git a/index.js b/index.js
index bdc80c6..8d050ad 100644
--- a/index.js
+++ b/index.js
@@ -2,7 +2,7 @@ const core = require("@actions/core");
 
 function parseVersion(str) {
   if (typeof str != "string") {
-    return false;
+    throw new Error("When parsing a version number a string is expected.");
   }
 
   var arr = str.split(".");