diff --git a/backend/idset.go b/backend/idset.go
index 817f80fff..b34a69afb 100644
--- a/backend/idset.go
+++ b/backend/idset.go
@@ -66,5 +66,5 @@ func (s IDSet) String() string {
 		return "{}"
 	}
 
-	return "{" + str[1:len(str)-2] + "}"
+	return "{" + str[1:len(str)-1] + "}"
 }