diff --git a/.circleci/build_win.ps1 b/.circleci/build_win.ps1
index 3e0518a37..2681cf67d 100644
--- a/.circleci/build_win.ps1
+++ b/.circleci/build_win.ps1
@@ -10,7 +10,7 @@ else {
 	# Use last commit date rather than build date to avoid ending up with builds for
 	# different platforms having different version strings (and therefore producing different bytecode)
 	# if the CI is triggered just before midnight.
-	$last_commit_timestamp = git log -1 --date=unix --format=%ad HEAD
+	$last_commit_timestamp = git log -1 --date=unix --format=%cd HEAD
 	$last_commit_date = (Get-Date -Date "1970-01-01 00:00:00Z").toUniversalTime().addSeconds($last_commit_timestamp).ToString("yyyy.M.d")
 	-join("ci.", $last_commit_date) | out-file -encoding ascii prerelease.txt
 }