diff --git a/include/signal.h b/include/signal.h
index fa00c94119..7318a334d3 100644
--- a/include/signal.h
+++ b/include/signal.h
@@ -39,7 +39,6 @@
 
 #define MIN_SIGNO       1               /* Lowest valid signal number */
 #define MAX_SIGNO       63              /* Highest valid signal number */
-#define GOOD_SIGNO(s)   ((((unsigned)(s)) <= MAX_SIGNO))
 
 /* Definitions for "standard" signals */
 
@@ -236,7 +235,10 @@
 #  define SIG_HOLD      ((_sa_handler_t)1)   /* Used only with sigset() */
 #endif
 
-#define tkill(tid, signo)  tgkill((pid_t)-1, tid, signo)
+#define GOOD_SIGNO(s)     (((unsigned)(s)) <= MAX_SIGNO)
+#define UNCAUGHT_SIGNO(s) ((s) == SIGKILL || (s) == SIGSTOP)
+
+#define tkill(tid, signo) tgkill((pid_t)-1, tid, signo)
 
 /****************************************************************************
  * Public Types
diff --git a/libs/libc/signal/sig_set.c b/libs/libc/signal/sig_set.c
index 24b0fc34ee..3b78f6bc1f 100644
--- a/libs/libc/signal/sig_set.c
+++ b/libs/libc/signal/sig_set.c
@@ -101,7 +101,7 @@ _sa_handler_t sigset(int signo, _sa_handler_t func)
   sigset_t set;
   int ret = -EINVAL;
 
-  if (signo == SIGKILL || signo == SIGSTOP || !GOOD_SIGNO(signo))
+  if (!GOOD_SIGNO(signo) || UNCAUGHT_SIGNO(signo))
     {
       goto err;
     }
diff --git a/libs/libc/signal/sig_signal.c b/libs/libc/signal/sig_signal.c
index 5dbcf9faae..d16191042b 100644
--- a/libs/libc/signal/sig_signal.c
+++ b/libs/libc/signal/sig_signal.c
@@ -62,7 +62,7 @@ _sa_handler_t signal(int signo, _sa_handler_t func)
   struct sigaction oact;
   int ret = -EINVAL;
 
-  if (!GOOD_SIGNO(signo))
+  if (!GOOD_SIGNO(signo) || UNCAUGHT_SIGNO(signo))
     {
       goto err;
     }