diff --git a/klib/src/platform/linux/linux.def b/klib/src/platform/linux/linux.def
index 3b9d8138bef..41ce9d4fd90 100644
--- a/klib/src/platform/linux/linux.def
+++ b/klib/src/platform/linux/linux.def
@@ -35,6 +35,6 @@ headers = aio.h aliases.h a.out.h argp.h argz.h byteswap.h cpio.h crypt.h \
 
 headers.x86-64 = sys/debugreg.h sys/reg.h sys/io.h sys/perm.h sys/kdaemon.h
 
-compilerOpts = -D_ANSI_SOURCE -D_POSIX_SOURCE -D_BSD_SOURCE -D_XOPEN_SOURCE=700
+compilerOpts = -D_ANSI_SOURCE -D_POSIX_C_SOURCE=199309 -D_BSD_SOURCE -D_XOPEN_SOURCE=700
 depends = posix
 
diff --git a/klib/src/platform/linux/posix.def b/klib/src/platform/linux/posix.def
index c82ab3a0fa3..a624819a42a 100644
--- a/klib/src/platform/linux/posix.def
+++ b/klib/src/platform/linux/posix.def
@@ -12,7 +12,8 @@ headers = alloca.h ar.h assert.h complex.h dirent.h dlfcn.h err.h errno.h fcntl.
     sys/queue.h sys/select.h sys/shm.h sys/stat.h sys/socket.h \
     sys/time.h sys/times.h sys/utsname.h sys/wait.h
 
-compilerOpts = -D_ANSI_SOURCE -D_POSIX_SOURCE -D_BSD_SOURCE -D_XOPEN_SOURCE=700 -D__need_error_t
+compilerOpts = -D_ANSI_SOURCE -D_POSIX_C_SOURCE=199309 -D_BSD_SOURCE \
+               -D_XOPEN_SOURCE=700 -D__need_error_t
 linkerOpts = -lresolv -lm -lpthread -lutil -lcrypt -lrt
 excludedFunctions = bindresvport6 __p_section __res_nisourserver __res_npquery \
                     ns_sign ns_sign2 ns_sign_tcp ns_sign_tcp2 ns_sign_tcp_init \
@@ -68,4 +69,4 @@ static int init_sockets() {
 }
 
 static void deinit_sockets() {
-}
\ No newline at end of file
+}
diff --git a/klib/src/platform/linux/zlib.def b/klib/src/platform/linux/zlib.def
index f30d62ea21b..fec75a8c121 100644
--- a/klib/src/platform/linux/zlib.def
+++ b/klib/src/platform/linux/zlib.def
@@ -1,4 +1,5 @@
 package = platform.zlib
 headers = zconf.h zlib.h
+compilerOpts = -D_ANSI_SOURCE -D_POSIX_C_SOURCE=199309 -D_BSD_SOURCE -D_XOPEN_SOURCE=700
 linkerOpts = -lz
-depends = posix
\ No newline at end of file
+depends = posix