diff --git a/APIServer.go b/APIServer.go
index dd781e3..7e73ee8 100644
--- a/APIServer.go
+++ b/APIServer.go
@@ -496,6 +496,15 @@ func handleRacsInbound(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	if params["USN"] == "" {
+		logger.Printf("[ERR]  %s; %s; %#v; %s\r\n", r.RemoteAddr, r.RequestURI, params, rst["ErrMsg"])
+		rst["Result"] = "NG"
+		rst["ErrMsg"] = "racs.HandleInbound: Missing Parameter - USN"
+		w.WriteHeader(http.StatusBadRequest)
+		fmt.Fprintf(w, "%v", strings.ReplaceAll(fmt.Sprintf("%#v", rst), "map[string]string", ""))
+		return
+	}
+
 	if cfg.Settings.LogRequest {
 		logger.Printf("[MSG]  %s; %s; Request: %#v\r\n", addr, uri, params)
 	}
@@ -534,6 +543,15 @@ func handleRacsOutbound(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	if params["USN"] == "" {
+		logger.Printf("[ERR]  %s; %s; %#v; %s\r\n", r.RemoteAddr, r.RequestURI, params, rst["ErrMsg"])
+		rst["Result"] = "NG"
+		rst["ErrMsg"] = "racs.HandleInbound: Missing Parameter - USN"
+		w.WriteHeader(http.StatusBadRequest)
+		fmt.Fprintf(w, "%v", strings.ReplaceAll(fmt.Sprintf("%#v", rst), "map[string]string", ""))
+		return
+	}
+
 	if cfg.Settings.LogRequest {
 		logger.Printf("[MSG]  %s; %s; Request: %#v\r\n", addr, uri, params)
 	}
diff --git a/APIServer.yml b/APIServer.yml
index 7ee290b..6c3d3b4 100644
--- a/APIServer.yml
+++ b/APIServer.yml
@@ -13,8 +13,8 @@ MySQL:
   Database: ewsv3_f715
   User: apisvc
   Password: wcqte
-  IssuesTable: issues
   StorageTable: racs
+  IssuesTable: issues
   IssuesView: v_issues
   OfflineView: v_offline
 Remark: