diff --git a/src/libcore/marker.rs b/src/libcore/marker.rs
index 3f4ff7c2f437e..d9757d78dcebb 100644
--- a/src/libcore/marker.rs
+++ b/src/libcore/marker.rs
@@ -73,9 +73,9 @@ impl<T: ?Sized> !Send for *mut T { }
 /// impl Foo for Impl { }
 /// impl Bar for Impl { }
 ///
-/// let x: &Foo = &Impl;    // OK
-/// // let y: &Bar = &Impl; // error: the trait `Bar` cannot
-///                         // be made into an object
+/// let x: &dyn Foo = &Impl;    // OK
+/// // let y: &dyn Bar = &Impl; // error: the trait `Bar` cannot
+///                             // be made into an object
 /// ```
 ///
 /// [trait object]: ../../book/ch17-02-trait-objects.html
diff --git a/src/libcore/mem/mod.rs b/src/libcore/mem/mod.rs
index 770d1ca8e7501..e110e93a95412 100644
--- a/src/libcore/mem/mod.rs
+++ b/src/libcore/mem/mod.rs
@@ -510,6 +510,8 @@ pub fn swap<T>(x: &mut T, y: &mut T) {
 /// A simple example:
 ///
 /// ```
+/// #![feature(mem_take)]
+///
 /// use std::mem;
 ///
 /// let mut v: Vec<i32> = vec![1, 2];
@@ -540,7 +542,8 @@ pub fn swap<T>(x: &mut T, y: &mut T) {
 /// `self`, allowing it to be returned:
 ///
 /// ```
-/// # #![allow(dead_code)]
+/// #![feature(mem_take)]
+///
 /// use std::mem;
 ///
 /// # struct Buffer<T> { buf: Vec<T> }
diff --git a/src/libcore/raw.rs b/src/libcore/raw.rs
index 155429b0e4f54..75c329a7d6c10 100644
--- a/src/libcore/raw.rs
+++ b/src/libcore/raw.rs
@@ -53,7 +53,7 @@
 /// let value: i32 = 123;
 ///
 /// // let the compiler make a trait object
-/// let object: &Foo = &value;
+/// let object: &dyn Foo = &value;
 ///
 /// // look at the raw representation
 /// let raw_object: raw::TraitObject = unsafe { mem::transmute(object) };
@@ -65,7 +65,7 @@
 ///
 /// // construct a new object, pointing to a different `i32`, being
 /// // careful to use the `i32` vtable from `object`
-/// let synthesized: &Foo = unsafe {
+/// let synthesized: &dyn Foo = unsafe {
 ///      mem::transmute(raw::TraitObject {
 ///          data: &other_value as *const _ as *mut (),
 ///          vtable: raw_object.vtable,
diff --git a/src/librustdoc/config.rs b/src/librustdoc/config.rs
index 6b490f730afa0..67ca7f407d801 100644
--- a/src/librustdoc/config.rs
+++ b/src/librustdoc/config.rs
@@ -351,9 +351,6 @@ impl Options {
                             .unwrap_or_else(|| PathBuf::from("doc"));
         let mut cfgs = matches.opt_strs("cfg");
         cfgs.push("rustdoc".to_string());
-        if should_test {
-            cfgs.push("test".to_string());
-        }
 
         let extension_css = matches.opt_str("e").map(|s| PathBuf::from(&s));
 
diff --git a/src/test/rustdoc-ui/cfg-test.rs b/src/test/rustdoc-ui/cfg-test.rs
index e26034371f444..6112e9b30e837 100644
--- a/src/test/rustdoc-ui/cfg-test.rs
+++ b/src/test/rustdoc-ui/cfg-test.rs
@@ -2,12 +2,15 @@
 // compile-flags:--test
 // normalize-stdout-test: "src/test/rustdoc-ui" -> "$$DIR"
 
+// Crates like core have doctests gated on `cfg(not(test))` so we need to make
+// sure `cfg(test)` is not active when running `rustdoc --test`.
+
 /// this doctest will be ignored:
 ///
 /// ```
 /// assert!(false);
 /// ```
-#[cfg(not(test))]
+#[cfg(test)]
 pub struct Foo;
 
 /// this doctest will be tested:
@@ -15,5 +18,5 @@ pub struct Foo;
 /// ```
 /// assert!(true);
 /// ```
-#[cfg(test)]
+#[cfg(not(test))]
 pub struct Foo;
diff --git a/src/test/rustdoc-ui/cfg-test.stdout b/src/test/rustdoc-ui/cfg-test.stdout
index 30bb0038d1b8d..67873870e89b2 100644
--- a/src/test/rustdoc-ui/cfg-test.stdout
+++ b/src/test/rustdoc-ui/cfg-test.stdout
@@ -1,6 +1,6 @@
 
 running 1 test
-test $DIR/cfg-test.rs - Foo (line 15) ... ok
+test $DIR/cfg-test.rs - Foo (line 18) ... ok
 
 test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out