diff --git a/mk/main.mk b/mk/main.mk
index b85c7a5c581f2..90d3563240cd3 100644
--- a/mk/main.mk
+++ b/mk/main.mk
@@ -18,7 +18,7 @@ CFG_RELEASE_NUM=1.12.0
 # An optional number to put after the label, e.g. '.2' -> '-beta.2'
 # NB Make sure it starts with a dot to conform to semver pre-release
 # versions (section 9)
-CFG_PRERELEASE_VERSION=.5
+CFG_PRERELEASE_VERSION=.6
 
 ifeq ($(CFG_RELEASE_CHANNEL),stable)
 # This is the normal semver version string, e.g. "0.12.0", "0.12.0-nightly"
diff --git a/src/libcollections/string.rs b/src/libcollections/string.rs
index 788c838cd3fc8..1ba0319f2d7d9 100644
--- a/src/libcollections/string.rs
+++ b/src/libcollections/string.rs
@@ -1901,26 +1901,6 @@ impl Into<Vec<u8>> for String {
     }
 }
 
-#[stable(feature = "stringfromchars", since = "1.12.0")]
-impl<'a> From<&'a [char]> for String {
-    #[inline]
-    fn from(v: &'a [char]) -> String {
-        let mut s = String::with_capacity(v.len());
-        for c in v {
-            s.push(*c);
-        }
-        s
-    }
-}
-
-#[stable(feature = "stringfromchars", since = "1.12.0")]
-impl From<Vec<char>> for String {
-    #[inline]
-    fn from(v: Vec<char>) -> String {
-        String::from(v.as_slice())
-    }
-}
-
 #[stable(feature = "rust1", since = "1.0.0")]
 impl fmt::Write for String {
     #[inline]