diff --git a/synapse/metrics/metric.py b/synapse/metrics/metric.py
index fbba94e633..98d5ca7b6c 100644
--- a/synapse/metrics/metric.py
+++ b/synapse/metrics/metric.py
@@ -324,4 +324,4 @@ def _escape_character(m):
 def _escape_label_value(value):
     """Takes a label value and escapes quotes, newlines and backslashes
     """
-    return re.sub(r"([\n\"\\])", _escape_character, value)
+    return re.sub(r"([\n\"\\])", _escape_character, str(value))