diff --git a/libc/include/sys/stat.h b/libc/include/sys/stat.h
index a074401d..03e139be 100644
--- a/libc/include/sys/stat.h
+++ b/libc/include/sys/stat.h
@@ -18,6 +18,9 @@ extern "C"
     /* Change the mode bits of a file. */
     int chmod(const char* path, mode_t mode);
 
+    /* Change the mode bits of a file descriptor. */
+    int fchmod(int fd, mode_t mode);
+
 #pragma GCC push_options
 #pragma GCC diagnostic ignored "-Wshadow"
 
diff --git a/libc/include/unistd.h b/libc/include/unistd.h
index e1045d96..ce7c5ec3 100644
--- a/libc/include/unistd.h
+++ b/libc/include/unistd.h
@@ -14,6 +14,9 @@
 #define STDOUT_FILENO 1
 #define STDERR_FILENO 2
 
+#define _POSIX_CHOWN_RESTRICTED 200112L
+#define _POSIX_SHELL 200112L
+
 #ifdef __cplusplus
 extern "C"
 {
@@ -55,6 +58,9 @@ extern "C"
     /* Change the owner and group of a file. */
     int chown(const char* path, uid_t uid, gid_t gid);
 
+    /* Change the owner and group of a file descriptor. */
+    int fchown(int fd, uid_t uid, gid_t gid);
+
     /* Replace the current process with another one. On success, does not return. */
     int execv(const char* path, char* const* argv);
 
diff --git a/libc/src/sys/stat.cpp b/libc/src/sys/stat.cpp
index 06ddfecc..7a02a22d 100644
--- a/libc/src/sys/stat.cpp
+++ b/libc/src/sys/stat.cpp
@@ -18,6 +18,12 @@ extern "C"
         __errno_return(rc, int);
     }
 
+    int fchmod(int fd, mode_t mode)
+    {
+        long rc = syscall(SYS_fchmodat, fd, "", mode, AT_EMPTY_PATH);
+        __errno_return(rc, int);
+    }
+
     int stat(const char* path, struct stat* st)
     {
         long rc = syscall(SYS_fstatat, AT_FDCWD, path, st, 0);
diff --git a/libc/src/unistd.cpp b/libc/src/unistd.cpp
index 6fc7dce7..42c7296e 100644
--- a/libc/src/unistd.cpp
+++ b/libc/src/unistd.cpp
@@ -148,6 +148,12 @@ extern "C"
         __errno_return(rc, int);
     }
 
+    int fchown(int fd, uid_t uid, gid_t gid)
+    {
+        long rc = syscall(SYS_fchownat, fd, "", uid, gid, AT_EMPTY_PATH);
+        __errno_return(rc, int);
+    }
+
     int execv(const char* path, char* const* argv)
     {
         return execve(path, argv, environ);