diff --git a/fbchat/_exception.py b/fbchat/_exception.py
index 76aa047..b35466b 100644
--- a/fbchat/_exception.py
+++ b/fbchat/_exception.py
@@ -46,6 +46,11 @@ class ParseError(FacebookError):
         return msg.format(self.message, self.data)
 
 
+@attr.s(slots=True, auto_exc=True)
+class NotLoggedIn(FacebookError):
+    """Raised by Facebook if the client has been logged out."""
+
+
 @attr.s(slots=True, auto_exc=True)
 class ExternalError(FacebookError):
     """Base class for errors that Facebook return."""
@@ -86,13 +91,6 @@ class InvalidParameters(ExternalError):
     """
 
 
-@attr.s(slots=True, auto_exc=True)
-class NotLoggedIn(ExternalError):
-    """Raised by Facebook if the client has been logged out."""
-
-    code = attr.ib()
-
-
 @attr.s(slots=True, auto_exc=True)
 class PleaseRefresh(ExternalError):
     """Raised by Facebook if the client has been inactive for too long.
@@ -108,7 +106,7 @@ def handle_payload_error(j):
         return
     code = j["error"]
     if code == 1357001:
-        error_cls = NotLoggedIn
+        raise NotLoggedIn(j["errorSummary"])
     elif code == 1357004:
         error_cls = PleaseRefresh
     elif code in (1357031, 1545010, 1545003):
diff --git a/fbchat/_session.py b/fbchat/_session.py
index 6e34d67..2bedefc 100644
--- a/fbchat/_session.py
+++ b/fbchat/_session.py
@@ -308,7 +308,7 @@ class Session:
             # Fall back to searching with a regex
             res = FB_DTSG_REGEX.search(r.text)
             if not res:
-                raise ValueError("Failed loading session, could not find fb_dtsg")
+                raise _exception.NotLoggedIn("Could not find fb_dtsg")
             fb_dtsg = res.group(1)
 
         revision = int(r.text.split('"client_revision":', 1)[1].split(",", 1)[0])