diff --git a/packages/node_modules/@node-red/nodes/core/network/10-mqtt.html b/packages/node_modules/@node-red/nodes/core/network/10-mqtt.html
index 0bb1e12f8..5b1b1f799 100644
--- a/packages/node_modules/@node-red/nodes/core/network/10-mqtt.html
+++ b/packages/node_modules/@node-red/nodes/core/network/10-mqtt.html
@@ -489,17 +489,23 @@
             tls: {type:"tls-config",required: false,
                   label:RED._("node-red:mqtt.label.use-tls") },
             clientid: {value:"", validate: function(v, opt) {
-                var ok = false;
+                let ok = true;
                 if ($("#node-config-input-clientid").length) {
                     // Currently editing the node
-                    ok = $("#node-config-input-cleansession").is(":checked") || (v||"").length > 0;
+                    let needClientId = !$("#node-config-input-cleansession").is(":checked") || !$("#node-config-input-autoUnsubscribe").is(":checked")
+                    if (needClientId) {
+                        ok = (v||"").length > 0;
+                    }
                 } else {
-                    ok = (this.cleansession===undefined || this.cleansession) || (v||"").length > 0;
+                    let needClientId = !(this.cleansession===undefined || this.cleansession) || this.autoUnsubscribe;
+                    if (needClientId) {
+                        ok = (v||"").length > 0;
+                    }
                 }
-                if (ok) {
-                    return ok;
+                if (!ok) {
+                    return RED._("node-red:mqtt.errors.invalid-client-id");
                 }
-                return RED._("node-red:mqtt.errors.invalid-client-id");
+                return true;
             }},
             autoConnect: {value: true},
             usetls: {value: false},