diff --git a/Cargo.toml b/Cargo.toml
index a25505c..972243b 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -9,5 +9,9 @@ gcc = "0.3.3"
 
 [features]
 default = ["os", "valgrind"]
-os = []
+os = ["libc"]
 valgrind = []
+
+[dependencies.libc]
+version = "0.1.6"
+optional = true
diff --git a/src/lib.rs b/src/lib.rs
index 9126995..b22ce9c 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -3,7 +3,6 @@
 // See the LICENSE file included in this distribution.
 #![feature(no_std)]
 #![feature(asm, core)]
-#![feature(libc)]
 #![no_std]
 
 //! libfringe is a low-level green threading library.