diff --git a/README.md b/README.md
index 95970afd..314a57fd 100644
--- a/README.md
+++ b/README.md
@@ -74,8 +74,15 @@ pinned version of Rustc if you require compatibility with a specific version.
 
 ## Crate Features
 
-Rand is built with only the `std` feature enabled by default. The following
-optional features are available:
+Rand is built with the `std` and `rand_os` features enabled by default:
+
+-   `std` enables functionality dependent on the `std` lib and implies `alloc`
+    and `rand_os`
+-   `rand_os` enables the `rand_os` crate, `rngs::OsRng` and enables its usage;
+    the continued existance of this feature is not guaranteed so users are
+    encouraged to specify `std` instead
+
+The following optional features are available:
 
 - `alloc` can be used instead of `std` to provide `Vec` and `Box`.
 - `log` enables some logging via the `log` crate.
diff --git a/src/deprecated.rs b/src/deprecated.rs
index 76055c14..88eb09fc 100644
--- a/src/deprecated.rs
+++ b/src/deprecated.rs
@@ -291,45 +291,12 @@ impl SeedableRng for StdRng {
 impl CryptoRng for StdRng {}
 
 
-#[cfg(all(feature="std",
-          any(target_os = "linux", target_os = "android",
-              target_os = "netbsd",
-              target_os = "dragonfly",
-              target_os = "haiku",
-              target_os = "emscripten",
-              target_os = "solaris",
-              target_os = "cloudabi",
-              target_os = "macos", target_os = "ios",
-              target_os = "freebsd",
-              target_os = "openbsd", target_os = "bitrig",
-              target_os = "redox",
-              target_os = "fuchsia",
-              windows,
-              all(target_arch = "wasm32", feature = "stdweb"),
-              all(target_arch = "wasm32", feature = "wasm-bindgen"),
-)))]
+#[cfg(feature="rand_os")]
 #[derive(Clone, Debug)]
 #[deprecated(since="0.6.0", note="import with rand::rngs::OsRng instead")]
 pub struct OsRng(rngs::OsRng);
 
-#[cfg(all(feature="std",
-          any(target_os = "linux", target_os = "android",
-              target_os = "netbsd",
-              target_os = "dragonfly",
-              target_os = "haiku",
-              target_os = "emscripten",
-              target_os = "solaris",
-              target_os = "cloudabi",
-              target_os = "macos", target_os = "ios",
-              target_os = "freebsd",
-              target_os = "openbsd", target_os = "bitrig",
-              target_os = "redox",
-              target_os = "fuchsia",
-              windows,
-              all(target_arch = "wasm32", feature = "stdweb"),
-              all(target_arch = "wasm32", feature = "wasm-bindgen"),
-)))]
-#[cfg(feature="std")]
+#[cfg(feature="rand_os")]
 impl RngCore for OsRng {
     #[inline(always)]
     fn next_u32(&mut self) -> u32 {
@@ -352,48 +319,14 @@ impl RngCore for OsRng {
     }
 }
 
-#[cfg(all(feature="std",
-          any(target_os = "linux", target_os = "android",
-              target_os = "netbsd",
-              target_os = "dragonfly",
-              target_os = "haiku",
-              target_os = "emscripten",
-              target_os = "solaris",
-              target_os = "cloudabi",
-              target_os = "macos", target_os = "ios",
-              target_os = "freebsd",
-              target_os = "openbsd", target_os = "bitrig",
-              target_os = "redox",
-              target_os = "fuchsia",
-              windows,
-              all(target_arch = "wasm32", feature = "stdweb"),
-              all(target_arch = "wasm32", feature = "wasm-bindgen"),
-)))]
-#[cfg(feature="std")]
+#[cfg(feature="rand_os")]
 impl OsRng {
     pub fn new() -> Result<Self, Error> {
         rngs::OsRng::new().map(OsRng)
     }
 }
 
-#[cfg(all(feature="std",
-          any(target_os = "linux", target_os = "android",
-              target_os = "netbsd",
-              target_os = "dragonfly",
-              target_os = "haiku",
-              target_os = "emscripten",
-              target_os = "solaris",
-              target_os = "cloudabi",
-              target_os = "macos", target_os = "ios",
-              target_os = "freebsd",
-              target_os = "openbsd", target_os = "bitrig",
-              target_os = "redox",
-              target_os = "fuchsia",
-              windows,
-              all(target_arch = "wasm32", feature = "stdweb"),
-              all(target_arch = "wasm32", feature = "wasm-bindgen"),
-)))]
-#[cfg(feature="std")]
+#[cfg(feature="rand_os")]
 impl CryptoRng for OsRng {}
 
 
diff --git a/src/lib.rs b/src/lib.rs
index 2610643f..a8fd21c7 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -119,23 +119,7 @@ pub mod seq;
 #[cfg(feature="std")] #[doc(hidden)] pub use deprecated::EntropyRng;
 
 #[allow(deprecated)]
-#[cfg(all(feature="std",
-          any(target_os = "linux", target_os = "android",
-              target_os = "netbsd",
-              target_os = "dragonfly",
-              target_os = "haiku",
-              target_os = "emscripten",
-              target_os = "solaris",
-              target_os = "cloudabi",
-              target_os = "macos", target_os = "ios",
-              target_os = "freebsd",
-              target_os = "openbsd", target_os = "bitrig",
-              target_os = "redox",
-              target_os = "fuchsia",
-              windows,
-              all(target_arch = "wasm32", feature = "stdweb"),
-              all(target_arch = "wasm32", feature = "wasm-bindgen"),
-)))]
+#[cfg(feature="rand_os")]
 #[doc(hidden)]
 pub use deprecated::OsRng;
 
@@ -152,23 +136,7 @@ pub mod jitter {
     pub use rngs::TimerError;
 }
 #[allow(deprecated)]
-#[cfg(all(feature="std",
-          any(target_os = "linux", target_os = "android",
-              target_os = "netbsd",
-              target_os = "dragonfly",
-              target_os = "haiku",
-              target_os = "emscripten",
-              target_os = "solaris",
-              target_os = "cloudabi",
-              target_os = "macos", target_os = "ios",
-              target_os = "freebsd",
-              target_os = "openbsd", target_os = "bitrig",
-              target_os = "redox",
-              target_os = "fuchsia",
-              windows,
-              all(target_arch = "wasm32", feature = "stdweb"),
-              all(target_arch = "wasm32", feature = "wasm-bindgen"),
-)))]
+#[cfg(feature="rand_os")]
 #[doc(hidden)]
 pub mod os {
     pub use deprecated::OsRng;
diff --git a/src/rngs/entropy.rs b/src/rngs/entropy.rs
index 8736324a..372b4d75 100644
--- a/src/rngs/entropy.rs
+++ b/src/rngs/entropy.rs
@@ -191,43 +191,11 @@ impl EntropySource for NoSource {
 }
 
 
-#[cfg(all(feature="std",
-          any(target_os = "linux", target_os = "android",
-              target_os = "netbsd",
-              target_os = "dragonfly",
-              target_os = "haiku",
-              target_os = "emscripten",
-              target_os = "solaris",
-              target_os = "cloudabi",
-              target_os = "macos", target_os = "ios",
-              target_os = "freebsd",
-              target_os = "openbsd", target_os = "bitrig",
-              target_os = "redox",
-              target_os = "fuchsia",
-              windows,
-              all(target_arch = "wasm32", feature = "stdweb"),
-              all(target_arch = "wasm32", feature = "wasm-bindgen"),
-)))]
+#[cfg(feature="rand_os")]
 #[derive(Clone, Debug)]
 pub struct Os(rngs::OsRng);
 
-#[cfg(all(feature="std",
-          any(target_os = "linux", target_os = "android",
-              target_os = "netbsd",
-              target_os = "dragonfly",
-              target_os = "haiku",
-              target_os = "emscripten",
-              target_os = "solaris",
-              target_os = "cloudabi",
-              target_os = "macos", target_os = "ios",
-              target_os = "freebsd",
-              target_os = "openbsd", target_os = "bitrig",
-              target_os = "redox",
-              target_os = "fuchsia",
-              windows,
-              all(target_arch = "wasm32", feature = "stdweb"),
-              all(target_arch = "wasm32", feature = "wasm-bindgen"),
-)))]
+#[cfg(feature="rand_os")]
 impl EntropySource for Os {
     fn new_and_fill(dest: &mut [u8]) -> Result<Self, Error> {
         let mut rng = rngs::OsRng::new()?;
@@ -240,23 +208,7 @@ impl EntropySource for Os {
     }
 }
 
-#[cfg(not(all(feature="std",
-              any(target_os = "linux", target_os = "android",
-                  target_os = "netbsd",
-                  target_os = "dragonfly",
-                  target_os = "haiku",
-                  target_os = "emscripten",
-                  target_os = "solaris",
-                  target_os = "cloudabi",
-                  target_os = "macos", target_os = "ios",
-                  target_os = "freebsd",
-                  target_os = "openbsd", target_os = "bitrig",
-                  target_os = "redox",
-                  target_os = "fuchsia",
-                  windows,
-                  all(target_arch = "wasm32", feature = "stdweb"),
-                  all(target_arch = "wasm32", feature = "wasm-bindgen"),
-))))]
+#[cfg(not(feature="std"))]
 type Os = NoSource;
 
 
diff --git a/src/rngs/mod.rs b/src/rngs/mod.rs
index 528e24d4..847fc943 100644
--- a/src/rngs/mod.rs
+++ b/src/rngs/mod.rs
@@ -178,5 +178,5 @@ pub use self::small::SmallRng;
 pub use self::std::StdRng;
 #[cfg(feature="std")] pub use self::thread::ThreadRng;
 
-#[cfg(feature="std")]
+#[cfg(feature="rand_os")]
 pub use rand_os::OsRng;