diff --git a/src/plugins/perfmon/intel/uncore.c b/src/plugins/perfmon/intel/uncore.c
index 8246bb1..4ed001d 100644
--- a/src/plugins/perfmon/intel/uncore.c
+++ b/src/plugins/perfmon/intel/uncore.c
@@ -78,7 +78,7 @@
 	{
 	  u8 *fmt = 0;
 
-	  fmt = format (0, "%s (%s)", unit_fmt, (n->unit_names[ubox]));
+	  fmt = format (0, "%s (%s)%c", unit_fmt, (n->unit_names[ubox]), 0);
 	  s = format (0, (char *) fmt, socket_id, ubox);
 	  vec_free (fmt);