diff --git a/tests/qemumonitorjsontest.c b/tests/qemumonitorjsontest.c
index 0574f8c6b993e4f6860b6f78a09dcce4240d5d58..993a373c31cb3c81b53d42e091e2d1a5a57aa6ad 100644
--- a/tests/qemumonitorjsontest.c
+++ b/tests/qemumonitorjsontest.c
@@ -753,7 +753,7 @@ qemuMonitorJSONTestAttachOneChardev(virDomainXMLOptionPtr xmlopt,
                                     bool fail)
 
 {
-    struct qemuMonitorJSONTestAttachChardevData data;
+    struct qemuMonitorJSONTestAttachChardevData data = {0};
     char *jsonreply = NULL;
     char *fulllabel = NULL;
     int ret = -1;