diff --git a/libmaxsi/include/unistd.h b/libmaxsi/include/unistd.h
index 49f2c160..527edd41 100644
--- a/libmaxsi/include/unistd.h
+++ b/libmaxsi/include/unistd.h
@@ -32,6 +32,14 @@
 #include <sortix/seek.h>
 #include <sortix/unistd.h>
 
+/* BSD compatibility: The problem with RFMEM is that isn't default to share, but
+   default to make a copy. However, Sortix rforks wants to make sharing default
+   and forking only happens if you ask for it. The Sortix RFFMEM extension
+   reverses this logic. */
+#if defined(RFMEM) && !defined(_BSD_SOURCE) && !defined(_WANT_RFMEM)
+#undef RFMEM
+#endif
+
 #define _SORTIX_ALWAYS_SBRK
 
 __BEGIN_DECLS
@@ -51,8 +59,6 @@ __BEGIN_DECLS
 
 @include(NULL.h)
 
-/* TODO: F_OK, R_OK, W_OK, X_OK is missing here. */
-
 /* TODO: _CS_* is missing here. */
 
 /* TODO: F_* is missing here. */
@@ -184,6 +190,7 @@ size_t pwriteall(int fd, const void* buf, size_t count, off_t off);
 size_t pwriteleast(int fd, const void* buf, size_t least, size_t max, off_t off);
 size_t readall(int fd, void* buf, size_t count);
 size_t readleast(int fd, void* buf, size_t least, size_t max);
+pid_t rfork(int flags);
 int uptime(uintmax_t* usecssinceboot);
 size_t writeall(int fd, const void* buf, size_t count);
 size_t writeleast(int fd, const void* buf, size_t least, size_t max);
diff --git a/libmaxsi/process.cpp b/libmaxsi/process.cpp
index 284e0e60..ab624d41 100644
--- a/libmaxsi/process.cpp
+++ b/libmaxsi/process.cpp
@@ -35,6 +35,7 @@ namespace Maxsi
 		DEFN_SYSCALL1_VOID(SysExit, SYSCALL_EXIT, int);
 		DEFN_SYSCALL3(int, SysExecVE, SYSCALL_EXEC, const char*, char* const*, char* const*);
 		DEFN_SYSCALL0(pid_t, SysFork, SYSCALL_FORK);
+		DEFN_SYSCALL1(pid_t, SysRFork, SYSCALL_RFORK, int);
 		DEFN_SYSCALL0(pid_t, SysGetPID, SYSCALL_GETPID);
 		DEFN_SYSCALL0(pid_t, SysGetParentPID, SYSCALL_GETPPID);
 		DEFN_SYSCALL3(pid_t, SysWait, SYSCALL_WAIT, pid_t, int*, int);
@@ -77,6 +78,11 @@ namespace Maxsi
 			return SysFork();
 		}
 
+		extern "C" int rfork(int flags)
+		{
+			return SysRFork(flags);
+		}
+
 		DUAL_FUNCTION(pid_t, getpid, GetPID, ())
 		{
 			return SysGetPID();
diff --git a/sortix/include/sortix/syscallnum.h b/sortix/include/sortix/syscallnum.h
index f88e4e1d..b5b0ccf5 100644
--- a/sortix/include/sortix/syscallnum.h
+++ b/sortix/include/sortix/syscallnum.h
@@ -74,7 +74,8 @@
 #define SYSCALL_KERNELINFO 48
 #define SYSCALL_PREAD 49
 #define SYSCALL_PWRITE 50
-#define SYSCALL_MAX_NUM 51 /* index of highest constant + 1 */
+#define SYSCALL_RFORK 51
+#define SYSCALL_MAX_NUM 52 /* index of highest constant + 1 */
 
 #endif
 
diff --git a/sortix/include/sortix/unistd.h b/sortix/include/sortix/unistd.h
index a163fcaf..443b0003 100644
--- a/sortix/include/sortix/unistd.h
+++ b/sortix/include/sortix/unistd.h
@@ -34,6 +34,17 @@ __BEGIN_DECLS
 #define X_OK 1 /* Test for execute permission. */
 #define F_OK 0 /* Test for existence. */
 
+#define RFCLONE (1<<0) /* Creates child, otherwise affect current process. */
+#define RFPID (1<<1) /* Allocates new PID. */
+#define RFFDG (1<<2) /* Fork file descriptor table. */
+#define RFMEM (1<<3) /* Shares address space. */
+#define RFFMEM (1<<4) /* Forks address space. */
+#define RFCWD (1<<5) /* Forks current directory pointer. */
+#define RFNS (1<<6) /* Forks namespace. */
+
+#define RFPROC (RFCLONE | RFPID | RFFMEM | RFCWD) /* Create new process. */
+#define RFFORK (RFPROC | RFFDG) /* Traditional fork(2) behavior. */
+
 __END_DECLS
 
 #endif
diff --git a/sortix/process.cpp b/sortix/process.cpp
index b79061b5..64100138 100644
--- a/sortix/process.cpp
+++ b/sortix/process.cpp
@@ -23,6 +23,7 @@
 ******************************************************************************/
 
 #include <sortix/kernel/platform.h>
+#include <sortix/unistd.h>
 #include <libmaxsi/error.h>
 #include <libmaxsi/memory.h>
 #include <libmaxsi/string.h>
@@ -431,8 +432,11 @@ namespace Sortix
 		return SysExevVEStage2(state);
 	}
 
-	pid_t SysFork()
+	pid_t SysRFork(int flags)
 	{
+		// TODO: Properly support rfork(2).
+		if ( flags != RFFORK ) { Error::Set(ENOSYS); return -1; }
+
 		// Prepare the state of the clone.
 		Syscall::SyscallRegs()->result = 0;
 		CurrentThread()->SaveRegisters(Syscall::InterruptRegs());
@@ -443,6 +447,11 @@ namespace Sortix
 		return clone->pid;
 	}
 
+	pid_t SysFork()
+	{
+		return SysRFork(RFFORK);
+	}
+
 	pid_t SysGetPID()
 	{
 		return CurrentProcess()->pid;
@@ -746,6 +755,7 @@ namespace Sortix
 	{
 		Syscall::Register(SYSCALL_EXEC, (void*) SysExecVE);
 		Syscall::Register(SYSCALL_FORK, (void*) SysFork);
+		Syscall::Register(SYSCALL_RFORK, (void*) SysRFork);
 		Syscall::Register(SYSCALL_GETPID, (void*) SysGetPID);
 		Syscall::Register(SYSCALL_GETPPID, (void*) SysGetParentPID);
 		Syscall::Register(SYSCALL_EXIT, (void*) SysExit);