diff --git a/src/capport/stats.py b/src/capport/stats.py
index f0d8a34..8d2692e 100644
--- a/src/capport/stats.py
+++ b/src/capport/stats.py
@@ -28,8 +28,8 @@ class MetricPrinter:
             self._now_str = ""
         labels = []
         if self.args.instance:
-            labels.append(f"instance={self.args.instance!r}")
-        labels.append(f"interface={self.args.interface!r}")
+            labels.append(f"instance=\"{self.args.instance}\"")
+        labels.append(f"interface=\"{self.args.interface}\"")
         self._label_str = "{" + ",".join(labels) + "}"
 
     def print_metric(self, *, name: str, mtype: str, value: typing.Any, help: str | None = None):