diff --git a/Cargo.toml b/Cargo.toml
index 695ab23..7aed107 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "redox_syscall"
-version = "0.1.46"
+version = "0.1.47"
 description = "A Rust library to access raw Redox system calls"
 license = "MIT"
 authors = ["Jeremy Soller <jackpot51@gmail.com>"]
diff --git a/src/call.rs b/src/call.rs
index 3b44185..cf89465 100644
--- a/src/call.rs
+++ b/src/call.rs
@@ -323,8 +323,10 @@ pub fn sigaction(sig: usize, act: Option<&SigAction>, oldact: Option<&mut SigAct
 }
 
 /// Get and/or set signal masks
-pub fn sigprocmask(how: usize, set: &[u64; 2], oset: &mut [u64; 2]) -> Result<usize> {
-    unsafe { syscall3(SYS_SIGPROCMASK, how, set.as_ptr() as usize, oset.as_mut_ptr() as usize) }
+pub fn sigprocmask(how: usize, set: Option<&[u64; 2]>, oldset: Option<&mut [u64; 2]>) -> Result<usize> {
+    unsafe { syscall3(SYS_SIGPROCMASK, how,
+                      set.map(|x| x as *const _).unwrap_or_else(ptr::null) as usize,
+                      oldset.map(|x| x as *mut _).unwrap_or_else(ptr::null_mut) as usize) }
 }
 
 // Return from signal handler