diff --git a/poetry.lock b/poetry.lock
index 5ffb592d835a..6956c651f41e 100644
--- a/poetry.lock
+++ b/poetry.lock
@@ -147,14 +147,14 @@ dev = ["Sphinx (==4.3.2)", "black (==22.3.0)", "build (==0.8.0)", "flake8 (==4.0
 
 [[package]]
 name = "canonicaljson"
-version = "1.6.4"
+version = "1.6.5"
 description = "Canonical JSON"
 category = "main"
 optional = false
 python-versions = ">=3.7"
 files = [
-    {file = "canonicaljson-1.6.4-py3-none-any.whl", hash = "sha256:55d282853b4245dbcd953fe54c39b91571813d7c44e1dbf66e3c4f97ff134a48"},
-    {file = "canonicaljson-1.6.4.tar.gz", hash = "sha256:6c09b2119511f30eb1126cfcd973a10824e20f1cfd25039cde3d1218dd9c8d8f"},
+    {file = "canonicaljson-1.6.5-py3-none-any.whl", hash = "sha256:806ea6f2cbb7405d20259e1c36dd1214ba5c242fa9165f5bd0bf2081f82c23fb"},
+    {file = "canonicaljson-1.6.5.tar.gz", hash = "sha256:68dfc157b011e07d94bf74b5d4ccc01958584ed942d9dfd5fdd706609e81cd4b"},
 ]
 
 [package.dependencies]
diff --git a/synapse/__init__.py b/synapse/__init__.py
index d2b8758f9689..fbfd506a43d0 100644
--- a/synapse/__init__.py
+++ b/synapse/__init__.py
@@ -64,9 +64,7 @@
 try:
     from canonicaljson import set_json_library
 
-    # type-ignore: I think there has been a regression in mypy 1.0.0 in how it checks
-    # modules against Protocols.
-    set_json_library(json)  # type: ignore[arg-type]
+    set_json_library(json)
 except ImportError:
     pass