diff --git a/src/application/Parser/Script/Compiler/Expressions/ExpressionsCompiler.ts b/src/application/Parser/Script/Compiler/Expressions/ExpressionsCompiler.ts
index a4898f47..8f8503cc 100644
--- a/src/application/Parser/Script/Compiler/Expressions/ExpressionsCompiler.ts
+++ b/src/application/Parser/Script/Compiler/Expressions/ExpressionsCompiler.ts
@@ -10,11 +10,14 @@ export class ExpressionsCompiler implements IExpressionsCompiler {
     public constructor(
         private readonly extractor: IExpressionParser = new CompositeExpressionParser()) { }
     public compileExpressions(
-        code: string,
+        code: string | undefined,
         args: IReadOnlyFunctionCallArgumentCollection): string {
         if (!args) {
             throw new Error('undefined args, send empty collection instead');
         }
+        if (!code) {
+            return code;
+        }
         const expressions = this.extractor.findExpressions(code);
         ensureParamsUsedInCodeHasArgsProvided(expressions, args);
         const context = new ExpressionEvaluationContext(args);
diff --git a/src/application/Parser/Script/Compiler/Expressions/IExpressionsCompiler.ts b/src/application/Parser/Script/Compiler/Expressions/IExpressionsCompiler.ts
index f73e8471..0703c20f 100644
--- a/src/application/Parser/Script/Compiler/Expressions/IExpressionsCompiler.ts
+++ b/src/application/Parser/Script/Compiler/Expressions/IExpressionsCompiler.ts
@@ -2,6 +2,6 @@ import { IReadOnlyFunctionCallArgumentCollection } from '../Function/Call/Argume
 
 export interface IExpressionsCompiler {
     compileExpressions(
-        code: string,
+        code: string | undefined,
         args: IReadOnlyFunctionCallArgumentCollection): string;
 }
diff --git a/src/application/Parser/Script/Compiler/Expressions/Parser/Regex/RegexParser.ts b/src/application/Parser/Script/Compiler/Expressions/Parser/Regex/RegexParser.ts
index 7e3eb178..3754bf20 100644
--- a/src/application/Parser/Script/Compiler/Expressions/Parser/Regex/RegexParser.ts
+++ b/src/application/Parser/Script/Compiler/Expressions/Parser/Regex/RegexParser.ts
@@ -15,6 +15,9 @@ export abstract class RegexParser implements IExpressionParser {
     protected abstract buildExpression(match: RegExpMatchArray): IPrimitiveExpression;
 
     private* findRegexExpressions(code: string): Iterable<IExpression> {
+        if (!code) {
+            throw new Error('undefined code');
+        }
         const matches = Array.from(code.matchAll(this.regex));
         for (const match of matches) {
             const startPos = match.index;
diff --git a/tests/unit/application/Parser/Script/Compiler/Expressions/ExpressionsCompiler.spec.ts b/tests/unit/application/Parser/Script/Compiler/Expressions/ExpressionsCompiler.spec.ts
index d89bcc77..1f893960 100644
--- a/tests/unit/application/Parser/Script/Compiler/Expressions/ExpressionsCompiler.spec.ts
+++ b/tests/unit/application/Parser/Script/Compiler/Expressions/ExpressionsCompiler.spec.ts
@@ -8,6 +8,28 @@ import { FunctionCallArgumentCollectionStub } from '@tests/unit/stubs/FunctionCa
 
 describe('ExpressionsCompiler', () => {
     describe('compileExpressions', () => {
+        describe('returns code when it is empty or undefined', () => {
+            // arrange
+            const testCases = [{
+                    name: 'empty',
+                    value: '',
+                }, {
+                    name: 'undefined',
+                    value: undefined,
+                },
+            ];
+            for (const test of testCases) {
+                it(`given ${test.name}`, () => {
+                    const expected = test.value;
+                    const sut = new SystemUnderTest();
+                    const args = new FunctionCallArgumentCollectionStub();
+                    // act
+                    const value = sut.compileExpressions(test.value, args);
+                    // assert
+                    expect(value).to.equal(expected);
+                });
+            }
+        });
         describe('combines expressions as expected', () => {
             // arrange
             const code = 'part1 {{ a }} part2 {{ b }} part3';
@@ -49,7 +71,7 @@ describe('ExpressionsCompiler', () => {
                     const expressionParserMock = new ExpressionParserStub()
                         .withResult(testCase.expressions);
                     const args = new FunctionCallArgumentCollectionStub();
-                    const sut = new MockableExpressionsCompiler(expressionParserMock);
+                    const sut = new SystemUnderTest(expressionParserMock);
                     // act
                     const actual = sut.compileExpressions(code, args);
                     // assert
@@ -69,7 +91,7 @@ describe('ExpressionsCompiler', () => {
                 ];
                 const expressionParserMock = new ExpressionParserStub()
                     .withResult(expressions);
-                const sut = new MockableExpressionsCompiler(expressionParserMock);
+                const sut = new SystemUnderTest(expressionParserMock);
                 // act
                 sut.compileExpressions(code, expected);
                 // assert
@@ -83,7 +105,7 @@ describe('ExpressionsCompiler', () => {
                 const expectedError = 'undefined args, send empty collection instead';
                 const args = undefined;
                 const expressionParserMock = new ExpressionParserStub();
-                const sut = new MockableExpressionsCompiler(expressionParserMock);
+                const sut = new SystemUnderTest(expressionParserMock);
                 // act
                 const act = () => sut.compileExpressions('code', args);
                 // assert
@@ -135,7 +157,7 @@ describe('ExpressionsCompiler', () => {
                     const code = 'non-important-code';
                     const expressionParserMock = new ExpressionParserStub()
                         .withResult(testCase.expressions);
-                    const sut = new MockableExpressionsCompiler(expressionParserMock);
+                    const sut = new SystemUnderTest(expressionParserMock);
                     // act
                     const act = () => sut.compileExpressions(code, testCase.args);
                     // assert
@@ -147,7 +169,7 @@ describe('ExpressionsCompiler', () => {
             // arrange
             const expected = 'expected-code';
             const expressionParserMock = new ExpressionParserStub();
-            const sut = new MockableExpressionsCompiler(expressionParserMock);
+            const sut = new SystemUnderTest(expressionParserMock);
             const args = new FunctionCallArgumentCollectionStub();
             // act
             sut.compileExpressions(expected, args);
@@ -158,8 +180,8 @@ describe('ExpressionsCompiler', () => {
     });
 });
 
-class MockableExpressionsCompiler extends ExpressionsCompiler {
-    constructor(extractor: IExpressionParser) {
+class SystemUnderTest extends ExpressionsCompiler {
+    constructor(extractor: IExpressionParser = new ExpressionParserStub()) {
         super(extractor);
     }
 }
diff --git a/tests/unit/application/Parser/Script/Compiler/Expressions/Parser/Regex/RegexParser.spec.ts b/tests/unit/application/Parser/Script/Compiler/Expressions/Parser/Regex/RegexParser.spec.ts
index e7f47a84..ac94bebb 100644
--- a/tests/unit/application/Parser/Script/Compiler/Expressions/Parser/Regex/RegexParser.spec.ts
+++ b/tests/unit/application/Parser/Script/Compiler/Expressions/Parser/Regex/RegexParser.spec.ts
@@ -7,6 +7,30 @@ import { FunctionParameterStub } from '@tests/unit/stubs/FunctionParameterStub';
 
 describe('RegexParser', () => {
     describe('findExpressions', () => {
+        describe('throws when code is unexpected', () => {
+            // arrange
+            const testCases = [
+                {
+                    name: 'undefined',
+                    value: undefined,
+                    expectedError: 'undefined code',
+                },
+                {
+                    name: 'empty',
+                    value: '',
+                    expectedError: 'undefined code',
+                },
+            ];
+            for (const testCase of testCases) {
+                it(`given ${testCase.name}`, () => {
+                    const sut = new RegexParserConcrete(/unimportant/);
+                    // act
+                    const act = () => sut.findExpressions(testCase.value);
+                    // assert
+                    expect(act).to.throw(testCase.expectedError);
+                });
+            }
+        });
         describe('matches regex as expected', () => {
             // arrange
             const testCases = [