diff --git a/src/functionsfactory.ts b/src/functionsfactory.ts
index 3dbace39ee..fb46bc3057 100644
--- a/src/functionsfactory.ts
+++ b/src/functionsfactory.ts
@@ -371,4 +371,15 @@ function propertyValue(params: any[]): any {
   const q = getQuestionValueByContext(this, params[0]);
   return q ? q[params[1]] : undefined;
 }
-FunctionFactory.Instance.register("propertyValue", propertyValue);
\ No newline at end of file
+FunctionFactory.Instance.register("propertyValue", propertyValue);
+function substring_(params: any[]): any {
+  if(params.length < 2) return "";
+  const s = params[0];
+  if(!s || typeof s !== "string") return "";
+  const start = params[1];
+  if(!Helpers.isNumber(start)) return "";
+  const end = params.length > 2 ? params[2] : undefined;
+  if(!Helpers.isNumber(end)) return s.substring(start);
+  return s.substring(start, end);
+}
+FunctionFactory.Instance.register("substring", substring_);
\ No newline at end of file
diff --git a/tests/expressions/expressionParserTest.ts b/tests/expressions/expressionParserTest.ts
index ed826bd82a..227d78599e 100644
--- a/tests/expressions/expressionParserTest.ts
+++ b/tests/expressions/expressionParserTest.ts
@@ -1509,3 +1509,12 @@ QUnit.test("Custom function returns object&array, #7050", function(assert) {
   FunctionFactory.Instance.unregister("func1");
   FunctionFactory.Instance.unregister("func2");
 });
+QUnit.test("ExpressionRunner: substring", function(assert) {
+  var runner = new ExpressionRunner("substring({s}, 1, 3)");
+  const values: any = { s: "abcdef" };
+  assert.equal(runner.run(values), "bc", "abcdef");
+  values.s = undefined;
+  assert.equal(runner.run(values), "", "undefined");
+  values.s = 10;
+  assert.equal(runner.run(values), "", "10");
+});