diff --git a/src/libstd/ffi/c_str.rs b/src/libstd/ffi/c_str.rs
index d2a885dc7fe..c8d43bfcef0 100644
--- a/src/libstd/ffi/c_str.rs
+++ b/src/libstd/ffi/c_str.rs
@@ -522,6 +522,13 @@ impl ToOwned for CStr {
     }
 }
 
+#[unstable(feature = "cstring_asref", reason = "recently added", issue = "0")]
+impl<'a> From<&'a CStr> for CString {
+    fn from(s: &'a CStr) -> CString {
+        s.to_owned()
+    }
+}
+
 #[unstable(feature = "cstring_asref", reason = "recently added", issue = "0")]
 impl ops::Index<ops::RangeFull> for CString {
     type Output = CStr;
@@ -532,13 +539,6 @@ impl ops::Index<ops::RangeFull> for CString {
     }
 }
 
-#[unstable(feature = "cstring_asref", reason = "recently added", issue = "0")]
-impl<'a, T: ?Sized + AsRef<CStr>> From<&'a T> for CString {
-    fn from(s: &'a T) -> CString {
-        s.as_ref().to_owned()
-    }
-}
-
 #[unstable(feature = "cstring_asref", reason = "recently added", issue = "0")]
 impl AsRef<CStr> for CStr {
     fn as_ref(&self) -> &CStr {