diff --git a/changelog.d/7936.misc b/changelog.d/7936.misc
new file mode 100644
index 0000000000..4304bbdd25
--- /dev/null
+++ b/changelog.d/7936.misc
@@ -0,0 +1 @@
+Switch to the JSON implementation from the standard library and bump the minimum version of the canonicaljson library to 1.2.0.
diff --git a/synapse/__init__.py b/synapse/__init__.py
index 83ce2ae6f4..72c93f6c48 100644
--- a/synapse/__init__.py
+++ b/synapse/__init__.py
@@ -17,6 +17,7 @@
""" This is a reference implementation of a Matrix homeserver.
"""
+import json
import os
import sys
@@ -25,6 +26,9 @@ if sys.version_info < (3, 5):
print("Synapse requires Python 3.5 or above.")
sys.exit(1)
+# Twisted and canonicaljson will fail to import when this file is executed to
+# get the __version__ during a fresh install. That's OK and subsequent calls to
+# actually start Synapse will import these libraries fine.
try:
from twisted.internet import protocol
from twisted.internet.protocol import Factory
@@ -36,6 +40,14 @@ try:
except ImportError:
pass
+# Use the standard library json implementation instead of simplejson.
+try:
+ from canonicaljson import set_json_library
+
+ set_json_library(json)
+except ImportError:
+ pass
+
__version__ = "1.18.0rc2"
if bool(os.environ.get("SYNAPSE_TEST_PATCH_LOG_CONTEXTS", False)):
diff --git a/synapse/python_dependencies.py b/synapse/python_dependencies.py
index 8cfcdb0573..abea2be4ef 100644
--- a/synapse/python_dependencies.py
+++ b/synapse/python_dependencies.py
@@ -43,7 +43,7 @@ REQUIREMENTS = [
"jsonschema>=2.5.1",
"frozendict>=1",
"unpaddedbase64>=1.1.0",
- "canonicaljson>=1.1.3",
+ "canonicaljson>=1.2.0",
# we use the type definitions added in signedjson 1.1.
"signedjson>=1.1.0",
"pynacl>=1.2.1",
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