diff --git a/lib/SimpleSAML/Utils/Crypto.php b/lib/SimpleSAML/Utils/Crypto.php
index 681c7a8a124c7039bfe2d252670771a14c1c4af2..3b711f6e6c6e1e531e921293dd1486635e1663a3 100644
--- a/lib/SimpleSAML/Utils/Crypto.php
+++ b/lib/SimpleSAML/Utils/Crypto.php
@@ -429,7 +429,9 @@ class Crypto
             throw new \InvalidArgumentException('Invalid input parameters.');
         }
 
-        if (!is_null(password_get_info($password)['algo'])) {
+        // Prior to PHP 7.4 password_get_info() would set the algo to 0 instead of NULL when it's not detected
+        $info = password_get_info($password);
+        if ($info['algo'] !== null && $info['algo'] !== 0) {
             throw new Error\Exception("Cannot use a hash value for authentication.");
         }