diff --git a/src/signal/sighold.c b/src/signal/sighold.c
index 992812fd0cb0ba342c0ec6e04ad5fc3998022c46..cfa2306c12992f99122d1e18c9fc47ab235c0023 100644
--- a/src/signal/sighold.c
+++ b/src/signal/sighold.c
@@ -1,5 +1,4 @@
 #include <signal.h>
-#include <stddef.h>
 
 int sighold(int sig)
 {
@@ -7,5 +6,5 @@ int sighold(int sig)
 
 	sigemptyset(&mask);
 	if (sigaddset(&mask, sig) < 0) return -1;
-	return sigprocmask(SIG_BLOCK, &mask, NULL);
+	return sigprocmask(SIG_BLOCK, &mask, 0);
 }
diff --git a/src/signal/sigignore.c b/src/signal/sigignore.c
index 78bd747413d67cbf50aa0395b2b8bd58edc01fd1..5ba05e129de1f7dd4203ff8f4ac928cb8b674ac3 100644
--- a/src/signal/sigignore.c
+++ b/src/signal/sigignore.c
@@ -1,5 +1,4 @@
 #include <signal.h>
-#include <stddef.h>
 
 int sigignore(int sig)
 {
@@ -8,5 +7,5 @@ int sigignore(int sig)
 	sigemptyset(&sa.sa_mask);
 	sa.sa_handler = SIG_IGN;
 	sa.sa_flags = 0;
-	return sigaction(sig, &sa, NULL);
+	return sigaction(sig, &sa, 0);
 }
diff --git a/src/signal/siginterrupt.c b/src/signal/siginterrupt.c
index 94f92be6aae4b53d349ff12a291bac060aa2acd5..70063400325c0f74f82235ffc4b9440dd4e264f2 100644
--- a/src/signal/siginterrupt.c
+++ b/src/signal/siginterrupt.c
@@ -1,13 +1,12 @@
-#include <stddef.h>
 #include <signal.h>
 
 int siginterrupt(int sig, int flag)
 {
 	struct sigaction sa;
 
-	sigaction(sig, NULL, &sa);
+	sigaction(sig, 0, &sa);
 	if (flag) sa.sa_flags &= ~SA_RESTART;
 	else sa.sa_flags |= SA_RESTART;
 
-	return sigaction(sig, &sa, NULL);
+	return sigaction(sig, &sa, 0);
 }
diff --git a/src/signal/sigrelse.c b/src/signal/sigrelse.c
index 31c1a030fe52708925cdb8fe96a227ff1537210b..b4c5a00f15615d3ddd8edd78eb61adfac85fe58e 100644
--- a/src/signal/sigrelse.c
+++ b/src/signal/sigrelse.c
@@ -1,5 +1,4 @@
 #include <signal.h>
-#include <stddef.h>
 
 int sigrelse(int sig)
 {
@@ -7,5 +6,5 @@ int sigrelse(int sig)
 
 	sigemptyset(&mask);
 	if (sigaddset(&mask, sig) < 0) return -1;
-	return sigprocmask(SIG_UNBLOCK, &mask, NULL);
+	return sigprocmask(SIG_UNBLOCK, &mask, 0);
 }
diff --git a/src/signal/sigset.c b/src/signal/sigset.c
index cbe462847f70c5083038420595e78f2815428efb..0d7b4564677b8f18d0b10979eb937086cd952007 100644
--- a/src/signal/sigset.c
+++ b/src/signal/sigset.c
@@ -1,5 +1,4 @@
 #include <signal.h>
-#include <stddef.h>
 
 void (*sigset(int sig, void (*handler)(int)))(int)
 {
@@ -11,7 +10,7 @@ void (*sigset(int sig, void (*handler)(int)))(int)
 		return SIG_ERR;
 	
 	if (handler == SIG_HOLD) {
-		if (sigaction(sig, NULL, &sa_old) < 0)
+		if (sigaction(sig, 0, &sa_old) < 0)
 			return SIG_ERR;
 		if (sigprocmask(SIG_BLOCK, &mask, &mask) < 0)
 			return SIG_ERR;
diff --git a/src/signal/sigwait.c b/src/signal/sigwait.c
index 48a855bb0a25136caf691775fde1e29c23806d4e..c8822eea49837bfc732ca38a330af89bc8582288 100644
--- a/src/signal/sigwait.c
+++ b/src/signal/sigwait.c
@@ -1,10 +1,9 @@
 #include <signal.h>
-#include <stddef.h>
 
 int sigwait(const sigset_t *restrict mask, int *restrict sig)
 {
 	siginfo_t si;
-	if (sigtimedwait(mask, &si, NULL) < 0)
+	if (sigtimedwait(mask, &si, 0) < 0)
 		return -1;
 	*sig = si.si_signo;
 	return 0;
diff --git a/src/signal/sigwaitinfo.c b/src/signal/sigwaitinfo.c
index c7b164df058429d9ea95bf9f6278bec3a706e471..bb51f8b523e6a33cc996a36e61863e36df4a1757 100644
--- a/src/signal/sigwaitinfo.c
+++ b/src/signal/sigwaitinfo.c
@@ -1,7 +1,6 @@
 #include <signal.h>
-#include <stddef.h>
 
 int sigwaitinfo(const sigset_t *restrict mask, siginfo_t *restrict si)
 {
-	return sigtimedwait(mask, si, NULL);
+	return sigtimedwait(mask, si, 0);
 }