diff --git a/matrix_alertbot/alertmanager.py b/matrix_alertbot/alertmanager.py
index 00d3f28..778ad6d 100644
--- a/matrix_alertbot/alertmanager.py
+++ b/matrix_alertbot/alertmanager.py
@@ -126,5 +126,5 @@ class AlertmanagerClient:
 
             if not matcher.match(labels):
                 raise AlertMismatchError(
-                    f"Alert with label {labels[matcher.label]} does not match {matcher}"
+                    f"Alert with label {matcher.label}={labels[matcher.label]} does not match {matcher}"
                 )