diff --git a/examples/bootstrap.php b/examples/bootstrap.php
index 5a81d8f17..fca3a003a 100644
--- a/examples/bootstrap.php
+++ b/examples/bootstrap.php
@@ -25,7 +25,7 @@
 
 function env(string $var)
 {
-    if (!isset($_SERVER[$var])) {
+    if (!isset($_SERVER[$var]) || '' === $_SERVER[$var]) {
         printf('Please set the "%s" environment variable to run this example.', $var);
         exit(1);
     }