diff --git a/crypto/bio/bio_test.cc b/crypto/bio/bio_test.cc
index 3d78635e..eb54f7e1 100644
--- a/crypto/bio/bio_test.cc
+++ b/crypto/bio/bio_test.cc
@@ -12,10 +12,6 @@
  * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
  * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
 
-#if !defined(_POSIX_C_SOURCE)
-#define _POSIX_C_SOURCE 201410L
-#endif
-
 #include <algorithm>
 #include <string>
 
diff --git a/crypto/bio/printf.c b/crypto/bio/printf.c
index 28162e6d..4f9d8a18 100644
--- a/crypto/bio/printf.c
+++ b/crypto/bio/printf.c
@@ -54,10 +54,6 @@
  * copied and put under another distribution licence
  * [including the GNU Public Licence.] */
 
-#if !defined(_POSIX_C_SOURCE)
-#define _POSIX_C_SOURCE 201410L  // for snprintf, vprintf etc
-#endif
-
 #include <openssl/bio.h>
 
 #include <assert.h>
diff --git a/crypto/lhash/lhash_test.cc b/crypto/lhash/lhash_test.cc
index cc146e87..0859eeb6 100644
--- a/crypto/lhash/lhash_test.cc
+++ b/crypto/lhash/lhash_test.cc
@@ -12,10 +12,6 @@
  * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
  * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
 
-#if !defined(_POSIX_C_SOURCE)
-#define _POSIX_C_SOURCE 201410L
-#endif
-
 #include <openssl/lhash.h>
 
 #include <stdio.h>
diff --git a/crypto/mem.c b/crypto/mem.c
index 09f3159a..67f74b79 100644
--- a/crypto/mem.c
+++ b/crypto/mem.c
@@ -54,10 +54,6 @@
  * copied and put under another distribution licence
  * [including the GNU Public Licence.] */
 
-#if !defined(_POSIX_C_SOURCE)
-#define _POSIX_C_SOURCE 201410L  // needed for strdup, snprintf, vprintf etc
-#endif
-
 #include <openssl/mem.h>
 
 #include <assert.h>