diff --git a/src/os.rs b/src/os.rs
index ef96e313379..9504427d0ad 100644
--- a/src/os.rs
+++ b/src/os.rs
@@ -12,7 +12,7 @@
 //! generators.
 
 use std::fmt;
-use rand_core::{RngCore, Error, impls};
+use rand_core::{CryptoRng, RngCore, Error, impls};
 
 /// A random number generator that retrieves randomness straight from the
 /// operating system.
@@ -72,6 +72,8 @@ impl OsRng {
     }
 }
 
+impl CryptoRng for OsRng {}
+
 impl RngCore for OsRng {
     fn next_u32(&mut self) -> u32 {
         impls::next_u32_via_fill(self)