diff --git a/synapse/config/logger.py b/synapse/config/logger.py
index ad4e6e61c3bf..dcd3ed1dac12 100644
--- a/synapse/config/logger.py
+++ b/synapse/config/logger.py
@@ -71,7 +71,7 @@
     # will be a delay for INFO/DEBUG logs to get written, but WARNING/ERROR
     # logs will still be flushed immediately.
     buffer:
-        class: logging.handlers.MemoryHandler
+        class: synapse.logging.handlers.PeriodicallyFlushingMemoryHandler
         target: file
         # The capacity is the number of log lines that are buffered before
         # being written to disk. Increasing this will lead to better
@@ -79,6 +79,9 @@
         # be written to disk.
         capacity: 10
         flushLevel: 30  # Flush for WARNING logs as well
+        # The period of time, in seconds, between forced flushes.
+        # Messages will not be delayed for longer than this time.
+        period: 5
 
     # A handler that writes logs to stderr. Unused by default, but can be used
     # instead of "buffer" and "file" in the logger handlers.