diff --git a/headers/posix/stdlib.h b/headers/posix/stdlib.h
index 9ab024e472..5f5d586085 100644
--- a/headers/posix/stdlib.h
+++ b/headers/posix/stdlib.h
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 Haiku, Inc. All Rights Reserved.
+ * Copyright 2002-2021 Haiku, Inc. All rights reserved.
  * Distributed under the terms of the MIT License.
  */
 #ifndef _STDLIB_H_
@@ -49,9 +49,7 @@ extern void		*calloc(size_t numElements, size_t size);
 extern void		free(void *pointer);
 extern void		*malloc(size_t size);
 extern int		posix_memalign(void **_pointer, size_t alignment, size_t size);
-#ifdef _ISOC11_SOURCE
 extern void 	*aligned_alloc(size_t alignment, size_t size) _ALIGNED_BY_ARG(1);
-#endif
 extern void		*realloc(void *oldPointer, size_t newSize);
 
 /* process termination */