diff --git a/errors.go b/errors.go
index 09ac1d65..332dbec2 100644
--- a/errors.go
+++ b/errors.go
@@ -25,8 +25,12 @@ var (
 	ErrInvalidatedAuthorizeCode = stderr.New("Authorization code has ben invalidated")
 	// ErrSerializationFailure is an error indicating that the transactional capable storage could not guarantee
 	// consistency of Update & Delete operations on the same rows between multiple sessions.
-	ErrSerializationFailure = stderr.New("The request could not be completed due to concurrent access")
-	ErrUnknownRequest       = &RFC6749Error{
+	ErrSerializationFailure = &RFC6749Error{
+		ErrorField:       errUnknownErrorName,
+		DescriptionField: "The request could not be completed because another request is competing for the same resource.",
+		CodeField:        http.StatusConflict,
+	}
+	ErrUnknownRequest = &RFC6749Error{
 		ErrorField:       errUnknownErrorName,
 		DescriptionField: "The handler is not responsible for this request.",
 		CodeField:        http.StatusBadRequest,
diff --git a/handler/oauth2/flow_refresh.go b/handler/oauth2/flow_refresh.go
index 5bf68070..789f8d63 100644
--- a/handler/oauth2/flow_refresh.go
+++ b/handler/oauth2/flow_refresh.go
@@ -221,12 +221,14 @@ func (c *RefreshTokenGrantHandler) handleRefreshTokenEndpointStorageError(ctx co
 	if errors.Is(storageErr, fosite.ErrSerializationFailure) {
 		return errorsx.WithStack(fosite.ErrInvalidRequest.
 			WithDebugf(storageErr.Error()).
+			WithWrap(storageErr).
 			WithHint("Failed to refresh token because of multiple concurrent requests using the same token which is not allowed."))
 	}
 
 	if errors.Is(storageErr, fosite.ErrNotFound) || errors.Is(storageErr, fosite.ErrInactiveToken) {
 		return errorsx.WithStack(fosite.ErrInvalidRequest.
 			WithDebugf(storageErr.Error()).
+			WithWrap(storageErr).
 			WithHint("Failed to refresh token because of multiple concurrent requests using the same token which is not allowed."))
 	}