diff --git a/.hgtags b/.hgtags
index c8359732c24b..cac5436c60d5 100644
--- a/.hgtags
+++ b/.hgtags
@@ -181,3 +181,4 @@ f53ecf8eee2a0d2a7705d7ea3ec8682028e922a0 FIREFOX_NIGHTLY_74_END
 3cc678e923e6f105437db28740c8223fd4940c8d FIREFOX_NIGHTLY_76_END
 200615cdc7c34a7fdfb2f7ffba158dae2cbf49d5 FIREFOX_BETA_77_BASE
 5b8406a0446906d7228e5d745549b50a3496dc0f FIREFOX_NIGHTLY_77_END
+e4b11f027efc1f8c2710ae3f52487a8f10a8fb39 FIREFOX_BETA_78_BASE