diff --git a/src/ncp/ncp_spinel.cpp b/src/ncp/ncp_spinel.cpp
index a5d8891270f..be7e64c3127 100644
--- a/src/ncp/ncp_spinel.cpp
+++ b/src/ncp/ncp_spinel.cpp
@@ -190,7 +190,7 @@ void NcpSpinel::ThreadErasePersistentInfo(AsyncTaskPtr aAsyncTask)
 {
     otError      error = OT_ERROR_NONE;
     spinel_tid_t tid   = GetNextTid();
-    va_list      args;
+    va_list      args  = {};
 
     VerifyOrExit(mThreadErasePersistentInfoTask == nullptr, error = OT_ERROR_BUSY);