diff --git a/lib/rules/property-no-unknown/__tests__/index.js b/lib/rules/property-no-unknown/__tests__/index.js
index 14bc4cbb64..a5c6bb6900 100644
--- a/lib/rules/property-no-unknown/__tests__/index.js
+++ b/lib/rules/property-no-unknown/__tests__/index.js
@@ -124,6 +124,10 @@ testRule({
 			code: '.foo { transform+_: rotate(15deg); }',
 			description: 'Append property value with space using +_',
 		},
+		{
+			code: '@foo: { prop: red; }',
+			description: 'ignore LESS map props',
+		},
 	],
 });
 
diff --git a/lib/utils/__tests__/isStandardSyntaxDeclaration.test.js b/lib/utils/__tests__/isStandardSyntaxDeclaration.test.js
index 3007100ace..7675150b89 100644
--- a/lib/utils/__tests__/isStandardSyntaxDeclaration.test.js
+++ b/lib/utils/__tests__/isStandardSyntaxDeclaration.test.js
@@ -134,6 +134,10 @@ describe('isStandardSyntaxDeclaration', () => {
 	it('less &:extend', () => {
 		expect(isStandardSyntaxDeclaration(lessDecl('a { &:extend(b) }'))).toBe(false);
 	});
+
+	it('less map', () => {
+		expect(isStandardSyntaxDeclaration(lessDecl('@map: { key: value; }'))).toBe(false);
+	});
 });
 
 function decl(css, parser = postcss) {
diff --git a/lib/utils/isStandardSyntaxDeclaration.js b/lib/utils/isStandardSyntaxDeclaration.js
index 22380cfe04..0552a69138 100644
--- a/lib/utils/isStandardSyntaxDeclaration.js
+++ b/lib/utils/isStandardSyntaxDeclaration.js
@@ -41,6 +41,11 @@ module.exports = function (decl) {
 		return false;
 	}
 
+	// Less map declaration
+	if (parent && parent.type === 'atrule' && parent.raws.afterName === ':') {
+		return false;
+	}
+
 	// Sass nested properties (e.g. border: { style: solid; color: red; })
 	if (
 		// @ts-ignore TODO TYPES selector does not exists