diff --git a/changelog.d/4138.misc b/changelog.d/4138.misc
new file mode 100644
index 000000000000..300199f8e8b2
--- /dev/null
+++ b/changelog.d/4138.misc
@@ -0,0 +1 @@
+The default logging config will now set an explicit log file encoding of UTF-8.
diff --git a/synapse/config/logger.py b/synapse/config/logger.py
index e9a936118d85..7081868963d4 100644
--- a/synapse/config/logger.py
+++ b/synapse/config/logger.py
@@ -50,6 +50,7 @@
         maxBytes: 104857600
         backupCount: 10
         filters: [context]
+        encoding: utf8
     console:
         class: logging.StreamHandler
         formatter: precise