diff --git a/include/roaring/portability.h b/include/roaring/portability.h
index 52d7b8f5..03e741b5 100644
--- a/include/roaring/portability.h
+++ b/include/roaring/portability.h
@@ -49,20 +49,6 @@
 #define CROARING_REGULAR_VISUAL_STUDIO 0
 #endif
 
-#if defined(_POSIX_C_SOURCE) && (_POSIX_C_SOURCE < 200809L)
-#undef _POSIX_C_SOURCE
-#endif
-
-#ifndef _POSIX_C_SOURCE
-#define _POSIX_C_SOURCE 200809L
-#endif  // !(defined(_POSIX_C_SOURCE)) || (_POSIX_C_SOURCE < 200809L)
-
-#ifdef __illumos__
-#ifndef __EXTENSIONS__
-#define __EXTENSIONS__
-#endif  // __EXTENSIONS__
-#endif
-
 #include <stdbool.h>
 #include <stdint.h>
 #include <stdlib.h>  // will provide posix_memalign with _POSIX_C_SOURCE as defined above
diff --git a/src/containers/bitset.c b/src/containers/bitset.c
index 7a38d072..b66f8807 100644
--- a/src/containers/bitset.c
+++ b/src/containers/bitset.c
@@ -2,9 +2,6 @@
  * bitset.c
  *
  */
-#ifndef _POSIX_C_SOURCE
-#define _POSIX_C_SOURCE 200809L
-#endif
 #include <assert.h>
 #include <stdio.h>
 #include <stdlib.h>