diff --git a/CHANGES.md b/CHANGES.md
index 38906ade49..8368ac0b92 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,5 +1,5 @@
-Synapse 1.21.0 (2020-10-01)
-===========================
+Synapse 1.21.0rc1 (2020-10-01)
+==============================
 
 Features
 --------
diff --git a/synapse/__init__.py b/synapse/__init__.py
index 57f818125a..4706974508 100644
--- a/synapse/__init__.py
+++ b/synapse/__init__.py
@@ -48,7 +48,7 @@ try:
 except ImportError:
     pass
 
-__version__ = "1.21.0"
+__version__ = "1.21.0rc1"
 
 if bool(os.environ.get("SYNAPSE_TEST_PATCH_LOG_CONTEXTS", False)):
     # We import here so that we don't have to install a bunch of deps when