diff --git a/packages/csp-header/src/index.ts b/packages/csp-header/src/index.ts
index 2cac6d2..fe3fdd1 100644
--- a/packages/csp-header/src/index.ts
+++ b/packages/csp-header/src/index.ts
@@ -1,6 +1,9 @@
 import {
 	ALLOWED_DIRECTIVES,
 } from './constants/directives';
+import {
+	NONE
+} from './constants/values';
 import {
 	CSPHeaderParams,
 	CSPDirectives,
@@ -138,10 +141,18 @@ function mergeDirectiveRules(directiveValue1: CSPDirectiveValue = '', directiveV
 	}
 
 	if (Array.isArray(directiveValue1) && Array.isArray(directiveValue2)) {
-		return getUniqRules([
+		const uniqRules =  getUniqRules([
 			...directiveValue1,
 			...directiveValue2
 		]);
+
+		const noneIndex = uniqRules.indexOf(NONE);
+		// Remove "'none'" if there are other rules
+		if(noneIndex >= 0 && uniqRules.length > 1) {
+			uniqRules.splice(noneIndex, 1);
+		}
+
+		return uniqRules;
 	}
 
 	return directiveValue2;
diff --git a/packages/csp-header/tests/index.test.ts b/packages/csp-header/tests/index.test.ts
index f1e872f..7c46b70 100644
--- a/packages/csp-header/tests/index.test.ts
+++ b/packages/csp-header/tests/index.test.ts
@@ -1,4 +1,4 @@
-import { getCSP, CSPDirectiveName, CSPHeaderParams, nonce, SELF } from '../src';
+import {CSPDirectiveName, CSPHeaderParams, getCSP, nonce, NONE, SELF} from '../src';
 
 describe('CSP building', () => {
 	test('should correctly make policy with the only rule', () => {
@@ -107,6 +107,32 @@ describe('Presets', () => {
 			})).toBe('script-src domain1.com domain2.com;')
 		});
 
+		test('should remove \'none\' directive when merging with well-defined directive', () => {
+			expect(getCSP({
+				directives: {
+					'script-src': [ 'domain1.com' ]
+				},
+				presets: [
+					{
+						'script-src': [ NONE ]
+					}
+				]
+			})).toBe('script-src domain1.com;')
+		});
+
+		test('should remove \'none\' directive when merging with well-defined preset', () => {
+			expect(getCSP({
+				directives: {
+					'script-src': [ NONE ]
+				},
+				presets: [
+					{
+						'script-src': [ 'domain2.com' ]
+					}
+				]
+			})).toBe('script-src domain2.com;')
+		});
+
 		test('should work with empty policies', () => {
 			expect(getCSP({
 				directives: {},
@@ -206,6 +232,32 @@ describe('Presets', () => {
 			})).toBe('script-src domain1.com domain2.com;')
 		});
 
+		test('should remove \'none\' directive when merging with well-defined directive', () => {
+			expect(getCSP({
+				directives: {
+					'script-src': [ 'domain1.com' ]
+				},
+				presets: {
+					myPreset: {
+						'script-src': [ NONE ]
+					}
+				}
+			})).toBe('script-src domain1.com;')
+		});
+
+		test('should remove \'none\' directive when merging with well-defined preset', () => {
+			expect(getCSP({
+				directives: {
+					'script-src': [ NONE ]
+				},
+				presets: {
+					myPreset: {
+						'script-src': [ 'domain2.com' ]
+					}
+				}
+			})).toBe('script-src domain2.com;')
+		});
+
 		test('should work with empty policies', () => {
 			expect(getCSP({
 				directives: {},