diff --git a/.cirrus.yml b/.cirrus.yml
index 5223c0bea6a..4fad68831a6 100644
--- a/.cirrus.yml
+++ b/.cirrus.yml
@@ -107,6 +107,7 @@ task:
 
 task:
   name: 'x86_64 Linux  [GOAL: install]  [focal]  [no depends, only system libs, sanitizers: fuzzer,address,undefined]'
+  only_if: $CIRRUS_BRANCH == $CIRRUS_DEFAULT_BRANCH || $CIRRUS_BASE_BRANCH == $CIRRUS_DEFAULT_BRANCH
   << : *GLOBAL_TASK_TEMPLATE
   container:
     image: ubuntu:focal