diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index f5cc1ce..8dcb8f6 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -16,6 +16,7 @@
 #include <linux/smp_lock.h>
 #include <linux/ptrace.h>
 #include <linux/security.h>
+#include <linux/signal.h>
 
 #include <asm/pgtable.h>
 #include <asm/uaccess.h>
@@ -166,7 +167,7 @@
 
 int ptrace_detach(struct task_struct *child, unsigned int data)
 {
-	if ((unsigned long) data > _NSIG)
+	if (!valid_signal(data))
 		return	-EIO;
 
 	/* Architecture-specific hardware disable .. */