diff --git a/libraries/botframework-expressions/src/builtInFunction.ts b/libraries/botframework-expressions/src/builtInFunction.ts
index 2f2dbd7e0a..8a2767a1a0 100644
--- a/libraries/botframework-expressions/src/builtInFunction.ts
+++ b/libraries/botframework-expressions/src/builtInFunction.ts
@@ -1895,9 +1895,9 @@ export class BuiltInFunctions {
                 (expression: Expression): void => BuiltInFunctions.validateArityAndAnyType(expression, 3, 3, ReturnType.String)),
             new ExpressionEvaluator(
                 ExpressionType.Split,
-                BuiltInFunctions.apply((args: any []): string[] => BuiltInFunctions.parseStringOrNull(args[0]).split(BuiltInFunctions.parseStringOrNull(args[1])), BuiltInFunctions.verifyStringOrNull),
+                BuiltInFunctions.apply((args: any []): string[] => BuiltInFunctions.parseStringOrNull(args[0]).split(BuiltInFunctions.parseStringOrNull(args[1]? args[1]: '')), BuiltInFunctions.verifyStringOrNull),
                 ReturnType.Object,
-                (expression: Expression): void => BuiltInFunctions.validateArityAndAnyType(expression, 2, 2, ReturnType.String)),
+                (expression: Expression): void => BuiltInFunctions.validateArityAndAnyType(expression, 1, 2, ReturnType.String)),
             new ExpressionEvaluator(
                 ExpressionType.Substring,
                 BuiltInFunctions.substring,
diff --git a/libraries/botframework-expressions/tests/badExpression.test.js b/libraries/botframework-expressions/tests/badExpression.test.js
index 21514c7980..31f32ed5bb 100644
--- a/libraries/botframework-expressions/tests/badExpression.test.js
+++ b/libraries/botframework-expressions/tests/badExpression.test.js
@@ -46,7 +46,7 @@ const badExpressions =
       'replaceIgnoreCase(one, \'l\', \'k\')', // replaceIgnoreCase only accept string parameter
       'replaceIgnoreCase(\'hi\', 1, \'k\')', // replaceIgnoreCase only accept string parameter
       'replaceIgnoreCase(\'hi\', \'l\', 1)', // replaceIgnoreCase only accept string parameter
-      'split(hello)', // split need two parameters
+      'split(hello, \'l\',  \'l\')', // split need one or two parameters
       'split(one, \'l\')', // split only accept string parameter
       'split(hello, 1)', // split only accept string parameter
       'substring(hello, 0.5)', // the second parameter of substring must be integer
diff --git a/libraries/botframework-expressions/tests/expression.test.js b/libraries/botframework-expressions/tests/expression.test.js
index 598a3e32fe..e30e5a8949 100644
--- a/libraries/botframework-expressions/tests/expression.test.js
+++ b/libraries/botframework-expressions/tests/expression.test.js
@@ -93,6 +93,7 @@ const dataSource = [
     ['replaceIgnoreCase(nullObj, \'L\', \'k\')', ''],
     ['replaceIgnoreCase(\'hello\', \'L\', nullObj)', 'heo'],
     ['split(\'hello\',\'e\')', ['h', 'llo']],
+    ['split(\'hello\')', ['h', 'e', 'l', 'l', 'o']],
     ['split(nullObj,\'e\')', ['']],
     ['split(\'hello\',nullObj)', ['h', 'e', 'l', 'l', 'o']],
     ['split(nullObj,nullObj)', []],