diff --git a/games/snake.cpp b/games/snake.cpp
index c1ac17e1..bea1690e 100644
--- a/games/snake.cpp
+++ b/games/snake.cpp
@@ -56,8 +56,8 @@ void Reset()
 		case 3: velx = 0; vely = -1; break;
 	}
 
-	animalx = 2 + (rand() % width-4);
-	animaly = 2 + (rand() % height-4);
+	animalx = 2 + (rand() % (width-4));
+	animaly = 2 + (rand() % (height-4));
 
 	taillen = 0;
 	tailmax = 3;
@@ -141,8 +141,10 @@ void Update()
 	if ( newx == animalx && newy == animaly )
 	{
 		tailmax++;
-		animalx = 2 + (rand() % width-4);
-		animaly = 2 + (rand() % height-4);
+		animalx = 2 + (rand() % (width-4));
+		animaly = 2 + (rand() % (height-4));
+		ASSERT(0 <= animalx && animalx < width);
+		ASSERT(0 <= animaly && animaly < height);
 		if ( maxspeed < speed ) { speed += speedincrease; }
 	}
 
diff --git a/libmaxsi/c/hsrc/unistd.h b/libmaxsi/c/hsrc/unistd.h
index 3a1a7eac..bf96f74a 100644
--- a/libmaxsi/c/hsrc/unistd.h
+++ b/libmaxsi/c/hsrc/unistd.h
@@ -83,7 +83,6 @@ int chown(const char*, uid_t, gid_t);
 size_t confstr(int, char*, size_t);
 char* crypt(const char*, const char*);
 char* ctermid(char*);
-int dup(int);
 int dup2(int, int);
 void encrypt(char [64], int);
 int execl(const char*, const char*, ...);
@@ -159,6 +158,7 @@ extern int opterr, optind, optopt;
 #endif
 
 int close(int);
+int dup(int);
 void _exit(int);
 pid_t fork(void);
 pid_t getpid(void);
diff --git a/libmaxsi/io.cpp b/libmaxsi/io.cpp
index dfde5839..be89feab 100644
--- a/libmaxsi/io.cpp
+++ b/libmaxsi/io.cpp
@@ -34,6 +34,7 @@ namespace Maxsi
 	DEFN_SYSCALL3(ssize_t, SysWrite, 19, int, const void*, size_t);
 	DEFN_SYSCALL1(int, SysPipe, 20, int*);
 	DEFN_SYSCALL1(int, SysClose, 21, int);
+	DEFN_SYSCALL1(int, SysDup, 22, int);
 
 	size_t Print(const char* Message)
 	{
@@ -83,6 +84,11 @@ namespace Maxsi
 	{
 		return SysClose(fd);
 	}
+
+	extern "C" int dup(int fd)
+	{
+		return SysDup(fd);
+	}
 #endif
 
 }
diff --git a/libmaxsi/random.cpp b/libmaxsi/random.cpp
index 63daa8a4..9bbef8de 100644
--- a/libmaxsi/random.cpp
+++ b/libmaxsi/random.cpp
@@ -28,11 +28,11 @@ namespace Maxsi
 {
 	namespace Random
 	{
-		int random_seed=1337;
+		unsigned random_seed = 1337;
 		extern "C" int rand() 
 		{
 			random_seed = random_seed + 37 * 1103515245 + 12345;
-			return random_seed / 65536; 
+			return random_seed >> 16; 
 		}
 	}
 }
diff --git a/sortix/io.cpp b/sortix/io.cpp
index b7f362d3..e98df387 100644
--- a/sortix/io.cpp
+++ b/sortix/io.cpp
@@ -126,11 +126,21 @@ namespace Sortix
 			return 0;
 		}
 
+		int SysDup(int fd)
+		{
+			Process* process = CurrentProcess();
+			Device* dev = process->descriptors.Get(fd);
+			if ( !dev ) { return -1; /* TODO: EBADF */ }
+			process->descriptors.Free(fd);
+			return process->descriptors.Allocate(dev);
+		}
+
 		void Init()
 		{
 			Syscall::Register(SYSCALL_WRITE, (void*) SysWrite);
 			Syscall::Register(SYSCALL_READ, (void*) SysRead);
 			Syscall::Register(SYSCALL_CLOSE, (void*) SysClose);
+			Syscall::Register(SYSCALL_DUP, (void*) SysDup);
 		}
 	}
 }
diff --git a/sortix/syscallnum.h b/sortix/syscallnum.h
index f79ba6d0..a9678856 100644
--- a/sortix/syscallnum.h
+++ b/sortix/syscallnum.h
@@ -47,7 +47,8 @@
 #define SYSCALL_WRITE 19
 #define SYSCALL_PIPE 20
 #define SYSCALL_CLOSE 21
-#define SYSCALL_MAX_NUM 22 /* index of highest constant + 1 */
+#define SYSCALL_DUP 22
+#define SYSCALL_MAX_NUM 23 /* index of highest constant + 1 */
 
 #endif