diff --git a/src/call.rs b/src/call.rs
index 1b564cb..ee83143 100644
--- a/src/call.rs
+++ b/src/call.rs
@@ -327,6 +327,11 @@ pub fn sigreturn() -> Result<usize> {
     unsafe { syscall0(SYS_SIGRETURN) }
 }
 
+/// Set the file mode creation mask
+pub unsafe fn umask(mask: usize) -> Result<usize> {
+    syscall1(SYS_UMASK, mask)
+}
+
 /// Remove a file
 pub fn unlink<T: AsRef<[u8]>>(path: T) -> Result<usize> {
     unsafe { syscall2(SYS_UNLINK, path.as_ref().as_ptr() as usize, path.as_ref().len()) }
diff --git a/src/number.rs b/src/number.rs
index f8884aa..3a4407f 100644
--- a/src/number.rs
+++ b/src/number.rs
@@ -69,5 +69,6 @@ pub const SYS_SETRENS: usize =  952;
 pub const SYS_SETREUID: usize = 203;
 pub const SYS_SIGACTION: usize =67;
 pub const SYS_SIGRETURN: usize =119;
+pub const SYS_UMASK: usize =    60;
 pub const SYS_WAITPID: usize =  7;
 pub const SYS_YIELD: usize =    158;