diff --git a/src/conditions.ts b/src/conditions.ts
index 64ec65a5ce..7af6b8c04d 100644
--- a/src/conditions.ts
+++ b/src/conditions.ts
@@ -1,6 +1,6 @@
 import { HashTable } from "./helpers";
 import { ProcessValue } from "./conditionProcessValue";
-
+import { ConsoleWarnings } from "./console-warnings";
 import { Operand, FunctionOperand } from "./expressions/expressions";
 import { ConditionsParser } from "./conditionsParser";
 
@@ -90,8 +90,12 @@ export class ExpressionExecutor implements IExpresionExecutor {
     values: HashTable<any>,
     properties: HashTable<any> = null
   ): any {
-    if (!this.operand) return null;
-
+    if (!this.operand) {
+      if(!!this.expression) {
+        ConsoleWarnings.warn("Invalid expression: " + this.expression);
+      }
+      return null;
+    }
     this.processValue.values = values;
     this.processValue.properties = properties;
     if (!this.isAsync) return this.runValues();
diff --git a/src/functionsfactory.ts b/src/functionsfactory.ts
index f686d0b5cd..7f653c8b1a 100644
--- a/src/functionsfactory.ts
+++ b/src/functionsfactory.ts
@@ -1,5 +1,6 @@
 import { HashTable, Helpers } from "./helpers";
 import { settings } from "./settings";
+import { ConsoleWarnings } from "./console-warnings";
 
 export class FunctionFactory {
   public static Instance: FunctionFactory = new FunctionFactory();
@@ -41,7 +42,10 @@ export class FunctionFactory {
     properties: HashTable<any> = null
   ): any {
     var func = this.functionHash[name];
-    if (!func) return null;
+    if (!func) {
+      ConsoleWarnings.warn("Function name is unknown: " + name);
+      return null;
+    }
     let classRunner = {
       func: func,
     };
diff --git a/tests/expressions/expressionParserTest.ts b/tests/expressions/expressionParserTest.ts
index d1ea7cfcf0..4b59ef7dd5 100644
--- a/tests/expressions/expressionParserTest.ts
+++ b/tests/expressions/expressionParserTest.ts
@@ -7,7 +7,7 @@ import {
 import { ConditionRunner, ExpressionRunner } from "../../src/conditions";
 
 import { ConditionsParser } from "../../src/conditionsParser";
-
+import { ConsoleWarnings } from "../../src/console-warnings";
 import {
   Const,
   Variable,
@@ -1469,4 +1469,31 @@ QUnit.test("Sum two float numbers as string", function(assert) {
   let runner = new ExpressionRunner("{a} + {b}");
   assert.equal(runner.run({ a: "1.1", b: "2.2" }), 3.3, "#1");
   assert.equal(runner.run({ a: "0.1", b: "0.2" }), 0.3, "#2");
+});
+QUnit.test("Warn in console if the expression is invalid", function(assert) {
+  const prev = ConsoleWarnings.warn;
+  let reportText: string = "";
+  ConsoleWarnings.warn = (text: string) => {
+    reportText = text;
+  };
+  const runner = new ExpressionRunner("{a} ++");
+  assert.notOk(reportText);
+  runner.run({ a: 1 });
+  assert.equal(reportText, "Invalid expression: {a} ++");
+
+  reportText = "";
+  runner.expression = "{a} + 1";
+  runner.run({ a: 1 });
+  assert.notOk(reportText);
+
+  runner.expression = "tooday()";
+  assert.notOk(reportText);
+  runner.run({});
+  assert.equal(reportText, "Function name is unknown: tooday");
+
+  reportText = "";
+  runner.expression = "today";
+  runner.run({});
+  assert.notOk(reportText);
+  ConsoleWarnings.warn = prev;
 });
\ No newline at end of file