diff --git a/lack-session-store-dbi.asd b/lack-session-store-dbi.asd
index b7ac99e..3e44351 100644
--- a/lack-session-store-dbi.asd
+++ b/lack-session-store-dbi.asd
@@ -10,6 +10,7 @@
   :depends-on (:lack-middleware-session
                :dbi
                :marshal
+               :trivial-utf-8
                :cl-base64)
   :components ((:file "src/middleware/session/store/dbi"))
   :in-order-to ((test-op (test-op t-lack-session-store-dbi))))
diff --git a/src/middleware/session/store/dbi.lisp b/src/middleware/session/store/dbi.lisp
index 7b1b945..3fa6cf9 100644
--- a/src/middleware/session/store/dbi.lisp
+++ b/src/middleware/session/store/dbi.lisp
@@ -7,8 +7,11 @@
                 :marshal
                 :unmarshal)
   (:import-from :cl-base64
-                :base64-string-to-string
-                :string-to-base64-string)
+                :base64-string-to-usb8-array
+                :usb8-array-to-base64-string)
+  (:import-from :trivial-utf-8
+                :string-to-utf-8-bytes
+                :utf-8-bytes-to-string)
   (:export :dbi-store
            :make-dbi-store
            :fetch-session
@@ -19,9 +22,11 @@
 (defstruct (dbi-store (:include store))
   (connector nil :type function)
   (serializer (lambda (data)
-                (string-to-base64-string (prin1-to-string (marshal data)))))
+                (usb8-array-to-base64-string
+                 (string-to-utf-8-bytes (prin1-to-string (marshal data))))))
   (deserializer (lambda (data)
-                  (unmarshal (read-from-string (base64-string-to-string data)))))
+                  (unmarshal (read-from-string
+                              (utf-8-bytes-to-string (base64-string-to-usb8-array data))))))
   (table-name "sessions"))
 
 (defmethod fetch-session ((store dbi-store) sid)