diff --git a/tsdb/head.go b/tsdb/head.go
index 019991e0f..3a577763d 100644
--- a/tsdb/head.go
+++ b/tsdb/head.go
@@ -626,7 +626,7 @@ Outer:
 	}
 
 	if unknownRefs.Load() > 0 {
-		level.Warn(h.logger).Log("msg", "Unknown series references", "count", unknownRefs)
+		level.Warn(h.logger).Log("msg", "Unknown series references", "count", unknownRefs.Load())
 	}
 	return nil
 }