diff --git a/src/os.rs b/src/os.rs
index 809e34c78e3..f55ff4ad4de 100644
--- a/src/os.rs
+++ b/src/os.rs
@@ -53,7 +53,8 @@ fn next_u64(mut fill_buf: &mut FnMut(&mut [u8])) -> u64 {
 }
 
 #[cfg(all(unix, not(target_os = "ios"),
-          not(target_os = "nacl")))]
+          not(target_os = "nacl"),
+          not(target_os = "freebsd")))]
 mod imp {
     extern crate libc;
 
@@ -245,6 +246,49 @@ mod imp {
     }
 }
 
+#[cfg(target_os = "freebsd")]
+mod imp {
+    extern crate libc;
+
+    use std::{io, ptr};
+    use Rng;
+
+    use super::{next_u32, next_u64};
+
+    pub struct OsRng;
+
+    impl OsRng {
+        pub fn new() -> io::Result<OsRng> {
+            Ok(OsRng)
+        }
+    }
+
+    impl Rng for OsRng {
+        fn next_u32(&mut self) -> u32 {
+            next_u32(&mut |v| self.fill_bytes(v))
+        }
+        fn next_u64(&mut self) -> u64 {
+            next_u64(&mut |v| self.fill_bytes(v))
+        }
+        fn fill_bytes(&mut self, v: &mut [u8]) {
+            let mib = [libc::CTL_KERN, libc::KERN_ARND];
+            // kern.arandom permits a maximum buffer size of 256 bytes
+            for s in v.chunks_mut(256) {
+                let mut s_len = s.len();
+                let ret = unsafe {
+                    libc::sysctl(mib.as_ptr(), mib.len() as libc::c_uint,
+                                 s.as_mut_ptr() as *mut _, &mut s_len,
+                                 ptr::null(), 0)
+                };
+                if ret == -1 || s_len != s.len() {
+                    panic!("kern.arandom sysctl failed! (returned {}, s.len() {}, oldlenp {})",
+                           ret, s.len(), s_len);
+                }
+            }
+        }
+    }
+}
+
 #[cfg(windows)]
 mod imp {
     use std::io;