diff --git a/nodes/core/core/75-exec.js b/nodes/core/core/75-exec.js
index 5eecbfa88..43aa1c387 100644
--- a/nodes/core/core/75-exec.js
+++ b/nodes/core/core/75-exec.js
@@ -23,6 +23,7 @@ module.exports = function(RED) {
     function ExecNode(n) {
         RED.nodes.createNode(this,n);
         this.cmd = (n.command || "").trim();
+        if (n.addpay == undefined) { n.addpay = true; }
         this.addpay = n.addpay;
         this.append = (n.append || "").trim();
         this.useSpawn = n.useSpawn;
diff --git a/nodes/core/io/10-mqtt.js b/nodes/core/io/10-mqtt.js
index 6652ecd57..2d9b45c17 100644
--- a/nodes/core/io/10-mqtt.js
+++ b/nodes/core/io/10-mqtt.js
@@ -106,7 +106,7 @@ module.exports = function(RED) {
                 if (node.topic) {
                     msg.topic = node.topic;
                 }
-                if ((msg.hasOwnProperty("topic")) && (typeof msg.topic === "string") && (msg.topic !== "")) { // topic must exist
+                if (msg.hasOwnProperty("payload") && (msg.hasOwnProperty("topic")) && (typeof msg.topic === "string") && (msg.topic !== "")) { // topic must exist
                     this.client.publish(msg);  // send the message
                 }
                 else { node.warn("Invalid topic specified"); }
diff --git a/nodes/core/logic/10-switch.js b/nodes/core/logic/10-switch.js
index 0cd1dc626..420008b6b 100644
--- a/nodes/core/logic/10-switch.js
+++ b/nodes/core/logic/10-switch.js
@@ -28,8 +28,8 @@ module.exports = function(RED) {
         'regex': function(a, b) { return (a + "").match(new RegExp(b)); },
         'true': function(a) { return a === true; },
         'false': function(a) { return a === false; },
-        'null': function(a) { return typeof a == "undefined"; },
-        'nnull': function(a) { return typeof a != "undefined"; },
+        'null': function(a) { return (typeof a == "undefined" || a === null); },
+        'nnull': function(a) { return (typeof a != "undefined" && a !== null); },
         'else': function(a) { return a === true; }
     };