diff --git a/lib/galaxy/tool_util/linters/output.py b/lib/galaxy/tool_util/linters/output.py
index 4068bf4d9d42..6323865db868 100644
--- a/lib/galaxy/tool_util/linters/output.py
+++ b/lib/galaxy/tool_util/linters/output.py
@@ -83,7 +83,6 @@ def lint(cls, tool_source: "ToolSource", lint_ctx: "LintContext"):
         tool_xml = getattr(tool_source, "xml_tree", None)
         if not tool_xml:
             return
-        labels = set()
         for filter in tool_xml.findall("./outputs//filter"):
             try:
                 ast.parse(filter.text, mode="eval")