diff --git a/CLOBBER b/CLOBBER
index 76c565a589d6..57ca408a475e 100644
--- a/CLOBBER
+++ b/CLOBBER
@@ -22,4 +22,4 @@
 # changes to stick? As of bug 928195, this shouldn't be necessary! Please
 # don't change CLOBBER for WebIDL changes any more.
 
-Modified build files in third_party/libwebrtc - Bug 1855330 - pt4 - BUILD.gn fixes for updated libwebrtc/third_party. r?ng!
+Merge day clobber 2023-10-23
\ No newline at end of file
diff --git a/browser/config/version.txt b/browser/config/version.txt
index f5d18d2f71bc..ff40f6958029 100644
--- a/browser/config/version.txt
+++ b/browser/config/version.txt
@@ -1 +1 @@
-120.0a1
+121.0a1
diff --git a/browser/config/version_display.txt b/browser/config/version_display.txt
index f5d18d2f71bc..ff40f6958029 100644
--- a/browser/config/version_display.txt
+++ b/browser/config/version_display.txt
@@ -1 +1 @@
-120.0a1
+121.0a1
diff --git a/config/milestone.txt b/config/milestone.txt
index df7d85faf041..d7d8d3dc3ff4 100644
--- a/config/milestone.txt
+++ b/config/milestone.txt
@@ -10,4 +10,4 @@
 # hardcoded milestones in the tree from these two files.
 #--------------------------------------------------------
 
-120.0a1
+121.0a1
diff --git a/services/sync/modules/constants.sys.mjs b/services/sync/modules/constants.sys.mjs
index c72d458b4521..7d895d0c5c71 100644
--- a/services/sync/modules/constants.sys.mjs
+++ b/services/sync/modules/constants.sys.mjs
@@ -4,7 +4,7 @@
 
 // Don't manually modify this line, as it is automatically replaced on merge day
 // by the gecko_migration.py script.
-export const WEAVE_VERSION = "1.122.0";
+export const WEAVE_VERSION = "1.123.0";
 
 // Sync Server API version that the client supports.
 export const SYNC_API_VERSION = "1.5";