diff --git a/.github/scripts/check_pr_title.py b/.github/scripts/check_pr_title.py
index dea47b763..3026e7acf 100644
--- a/.github/scripts/check_pr_title.py
+++ b/.github/scripts/check_pr_title.py
@@ -15,6 +15,7 @@
     "DEV: ",
     "STY: ",
     "MAINT: ",
+    "REL: ",  # For internal use only.
 )
 PR_TITLE = os.getenv("PR_TITLE", "")