diff --git a/cicd_tool/main.py b/cicd_tool/main.py
index 10341f1..4aa442e 100644
--- a/cicd_tool/main.py
+++ b/cicd_tool/main.py
@@ -183,7 +183,9 @@ def main(version: Optional[str] = None, app_dir: Optional[str] = None) -> None:
     if not artifact_base_url:
         raise ConfigurationError("ARTIFACT_BASE_URL is required")
 
-    bucket_name = os.environ.get("S3_BUCKET", "gitlite")
+    # S3/MinIO bucket names must be lowercase, so normalise regardless of how the
+    # S3_BUCKET variable is cased (e.g. "GitLite" -> "gitlite").
+    bucket_name = (os.environ.get("S3_BUCKET") or "gitlite").lower()
     bucket_prefix = (app_dir or os.environ.get("APP_DIR") or "gitlite").strip("/")
 
     artifacts = _collect_artifacts()