diff --git a/libraries/config/ServerConfigChecks.php b/libraries/config/ServerConfigChecks.php
index d97d702a18..5557a0f489 100644
--- a/libraries/config/ServerConfigChecks.php
+++ b/libraries/config/ServerConfigChecks.php
@@ -223,10 +223,12 @@ class ServerConfigChecks
                 $random_func = 'openssl_random_pseudo_bytes';
             }
             while (strlen($blowfishSecret) < 32) {
-                $byte = $random_func(1);
+                // Get random byte and strip highest bit
+                // to get ASCII only range
+                $byte = ord($random_func(1)) & 0x7f;
                 // We want only ASCII chars
-                if (ord($byte) > 32 && ord($byte) < 127) {
-                    $blowfishSecret .= $byte;
+                if ($byte > 32) {
+                    $blowfishSecret .= chr($byte);
                 }
             }