diff --git a/src/python/errors.py b/src/python/errors.py
new file mode 100644
index 00000000..5821726d
--- /dev/null
+++ b/src/python/errors.py
@@ -0,0 +1,67 @@
+from dataclasses import dataclass, field
+from typing import Optional
+
+import nio
+
+
+@dataclass
+class MatrixError(Exception):
+    http_code: int = 400
+    m_code:    str = "M_UNKNOWN"
+
+    @classmethod
+    def from_nio(cls, response: nio.ErrorResponse) -> "MatrixError":
+        # Check for the M_CODE first: some errors for an API share the same
+        # http code, but have different M_CODEs (e.g. POST /login 403).
+        for subcls in cls.__subclasses__():
+            if subcls.m_code == response.status_code:
+                return subcls()
+
+        for subcls in cls.__subclasses__():
+            if subcls.http_code == response.transport_response.status:
+                return subcls()
+
+        return cls(response.transport_response.status, response.status_code)
+
+
+@dataclass
+class MatrixForbidden(MatrixError):
+    http_code: int = 403
+    m_code:    str = "M_FORBIDDEN"
+
+
+@dataclass
+class MatrixUserDeactivated(MatrixError):
+    http_code: int = 403
+    m_code:    str = "M_USER_DEACTIVATED"
+
+
+@dataclass
+class MatrixNotFound(MatrixError):
+    http_code: int = 404
+    m_code:    str = "M_NOT_FOUND"
+
+
+@dataclass
+class MatrixTooLarge(MatrixError):
+    http_code: int = 413
+    m_code:    str = "M_TOO_LARGE"
+
+
+@dataclass
+class UserNotFound(Exception):
+    user_id: str = field()
+
+
+@dataclass
+class InvalidUserInContext(Exception):
+    user_id: str = field()
+
+
+@dataclass
+class UneededThumbnail(Exception):
+    pass
+
+@dataclass
+class UnthumbnailableError(Exception):
+    exception: Optional[Exception] = None
diff --git a/src/python/matrix_client.py b/src/python/matrix_client.py
index 1277be37..78ed9afd 100644
--- a/src/python/matrix_client.py
+++ b/src/python/matrix_client.py
@@ -7,7 +7,6 @@ import platform
 import re
 import traceback
 from contextlib import suppress
-from dataclasses import dataclass, field
 from datetime import datetime
 from functools import partial
 from pathlib import Path
@@ -24,6 +23,10 @@ from pymediainfo import MediaInfo
 import nio
 
 from . import __about__, utils
+from .errors import (
+    InvalidUserInContext, MatrixError, UneededThumbnail, UnthumbnailableError,
+    UserNotFound,
+)
 from .html_filter import HTML_FILTER
 from .models.items import (
     Account, Event, Member, Room, TypeSpecifier, Upload, UploadStatus,
@@ -34,69 +37,6 @@ from .pyotherside_events import AlertRequested
 CryptDict = Dict[str, Any]
 
 
-@dataclass
-class MatrixError(Exception):
-    http_code: int = 400
-    m_code:    str = "M_UNKNOWN"
-
-    @classmethod
-    def from_nio(cls, response: nio.ErrorResponse) -> "MatrixError":
-        # Check for the M_CODE first: some errors for an API share the same
-        # http code, but have different M_CODEs (e.g. POST /login 403).
-        for subcls in cls.__subclasses__():
-            if subcls.m_code == response.status_code:
-                return subcls()
-
-        for subcls in cls.__subclasses__():
-            if subcls.http_code == response.transport_response.status:
-                return subcls()
-
-        return cls(response.transport_response.status, response.status_code)
-
-
-@dataclass
-class MatrixForbidden(MatrixError):
-    http_code: int = 403
-    m_code:    str = "M_FORBIDDEN"
-
-
-@dataclass
-class MatrixUserDeactivated(MatrixError):
-    http_code: int = 403
-    m_code:    str = "M_USER_DEACTIVATED"
-
-
-@dataclass
-class MatrixNotFound(MatrixError):
-    http_code: int = 404
-    m_code:    str = "M_NOT_FOUND"
-
-
-@dataclass
-class MatrixTooLarge(MatrixError):
-    http_code: int = 413
-    m_code:    str = "M_TOO_LARGE"
-
-
-@dataclass
-class UserNotFound(Exception):
-    user_id: str = field()
-
-
-@dataclass
-class InvalidUserInContext(Exception):
-    user_id: str = field()
-
-
-@dataclass
-class UneededThumbnail(Exception):
-    pass
-
-@dataclass
-class UnthumbnailableError(Exception):
-    exception: Optional[Exception] = None
-
-
 class MatrixClient(nio.AsyncClient):
     def __init__(self,
                  backend,