diff --git a/src/libcore/char.rs b/src/libcore/char.rs
index 010415b364a..ba9748eea71 100644
--- a/src/libcore/char.rs
+++ b/src/libcore/char.rs
@@ -139,6 +139,7 @@ pub fn from_digit(num: u32, radix: u32) -> Option<char> {
 // NB: the stabilization and documentation for this trait is in
 // unicode/char.rs, not here
 #[allow(missing_docs)] // docs in libunicode/u_char.rs
+#[doc(hidden)]
 pub trait CharExt {
     fn is_digit(self, radix: u32) -> bool;
     fn to_digit(self, radix: u32) -> Option<u32>;
diff --git a/src/libcore/num/mod.rs b/src/libcore/num/mod.rs
index 28e0bcf13dd..2a194766834 100644
--- a/src/libcore/num/mod.rs
+++ b/src/libcore/num/mod.rs
@@ -2476,6 +2476,7 @@ pub enum FpCategory {
 //               `unused_self`. Removing it requires #8888 to be fixed.
 #[unstable(feature = "core",
            reason = "distribution of methods between core/std is unclear")]
+#[doc(hidden)]
 pub trait Float
     : Copy + Clone
     + NumCast
diff --git a/src/libcore/slice.rs b/src/libcore/slice.rs
index 70e60adf64c..0e6acf0160d 100644
--- a/src/libcore/slice.rs
+++ b/src/libcore/slice.rs
@@ -63,6 +63,7 @@ use raw::Slice as RawSlice;
 
 /// Extension methods for slices.
 #[allow(missing_docs)] // docs in libcollections
+#[doc(hidden)]
 pub trait SliceExt {
     type Item;
 
diff --git a/src/libcore/str/mod.rs b/src/libcore/str/mod.rs
index 5c8b6a774cd..9bc760b56ec 100644
--- a/src/libcore/str/mod.rs
+++ b/src/libcore/str/mod.rs
@@ -1496,6 +1496,7 @@ impl<'a, S: ?Sized> Str for &'a S where S: Str {
 
 /// Methods for string slices
 #[allow(missing_docs)]
+#[doc(hidden)]
 pub trait StrExt {
     // NB there are no docs here are they're all located on the StrExt trait in
     // libcollections, not here.