diff --git a/src/preprocessor/preprocessor-grammar.pegjs b/src/preprocessor/preprocessor-grammar.pegjs
index c3f9094..610abeb 100644
--- a/src/preprocessor/preprocessor-grammar.pegjs
+++ b/src/preprocessor/preprocessor-grammar.pegjs
@@ -77,6 +77,7 @@ UNDEF = wsStart:_? token:"#undef" wsEnd:_? { return node('literal', { literal: t
 ERROR = wsStart:_? token:"#error" wsEnd:_? { return node('literal', { literal: token, wsStart, wsEnd }); }
 PRAGMA = wsStart:_? token:"#pragma" wsEnd:_? { return node('literal', { literal: token, wsStart, wsEnd }); }
 DEFINED = wsStart:_? token:"defined" wsEnd:_? { return node('literal', { literal: token, wsStart, wsEnd }); }
+DEFINED_WITH_END_WS = wsStart:_? token:"defined" wsEnd:whitespace { return node('literal', { literal: token, wsStart, wsEnd }); }
 IF = wsStart:_? token:"#if" wsEnd:_? { return node('literal', { literal: token, wsStart, wsEnd }); }
 IFDEF = wsStart:_? token:"#ifdef" wsEnd:_? { return node('literal', { literal: token, wsStart, wsEnd }); }
 IFNDEF = wsStart:_? token:"#ifndef" wsEnd:_? { return node('literal', { literal: token, wsStart, wsEnd }); }
@@ -224,8 +225,8 @@ unary_expression "unary expression"
   = operator:DEFINED lp:LEFT_PAREN identifier:IDENTIFIER rp:RIGHT_PAREN {
     return node('unary_defined', { operator, lp, identifier, rp, });
   }
-  / operator:DEFINED identifier:IDENTIFIER {
-    return node('unary_defined', { operator, identifier, });
+  / operator:DEFINED_WITH_END_WS identifier:IDENTIFIER {
+    return node('unary_defined', { operator, identifier});
   }
   / operator:(PLUS / DASH / BANG / TILDE)
     expression:unary_expression {
diff --git a/src/preprocessor/preprocessor.test.ts b/src/preprocessor/preprocessor.test.ts
index 9bd62df..0765cf5 100644
--- a/src/preprocessor/preprocessor.test.ts
+++ b/src/preprocessor/preprocessor.test.ts
@@ -5,6 +5,7 @@ import {
   preprocessComments,
   preprocessAst,
   PreprocessorProgram,
+  visitPreprocessedAst,
 } from './preprocessor.js';
 import generate from './generator.js';
 import { GlslSyntaxError } from '../error.js';
@@ -477,13 +478,32 @@ test('generate #ifdef & #ifndef & #else', () => {
 `);
 });
 
-test('generate defined', () => {
+
+test('parse defined', () => {
   expectParsedProgram(`
-#if defined AAA  && defined(BBB)
+#if defined AAA && defined(BBB)&& definedCCC
 #endif
 `);
 });
 
+test('parse definedXXX', () => {
+  const program = `
+#if definedXXX
+#endif
+`;
+  const ast = parse(program);
+  visitPreprocessedAst(ast, {
+    conditional: {
+      enter: function (path) {
+        if (path.node.ifPart.type === 'if') {
+          expect(path.node.ifPart.expression.type).toBe('identifier');
+        }
+      }
+    }
+  });
+  expectParsedProgram(program);
+});
+
 /*
 test('debug', () => {
   const program = `