diff --git a/build.rs b/build.rs
index 4dcf8e8..4f39b83 100644
--- a/build.rs
+++ b/build.rs
@@ -1,18 +1,19 @@
 extern crate autocfg;
 
-use autocfg::AutoCfg;
 use std::env;
 
 fn main() {
+    let autocfg = autocfg::new();
+
     // If the "i128" feature is explicity requested, don't bother probing for it.
     // It will still cause a build error if that was set improperly.
-    if env::var_os("CARGO_FEATURE_I128").is_some() || autocfg::new().probe_type("i128") {
+    if env::var_os("CARGO_FEATURE_I128").is_some() || autocfg.probe_type("i128") {
         autocfg::emit("has_i128");
     }
 
     // The RangeBounds trait was stabilized in 1.28, so from that version onwards we
     // implement that trait.
-    AutoCfg::new().unwrap().emit_rustc_version(1, 28);
+    autocfg.emit_rustc_version(1, 28);
 
     autocfg::rerun_path("build.rs");
 }
diff --git a/src/lib.rs b/src/lib.rs
index 58ce531..1689dee 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -22,11 +22,14 @@ extern crate std;
 extern crate num_integer as integer;
 extern crate num_traits as traits;
 
-use core::ops::{Add, Bound, RangeBounds, Sub};
+use core::ops::{Add, Sub};
 use core::usize;
 use integer::Integer;
 use traits::{CheckedAdd, One, ToPrimitive, Zero};
 
+#[cfg(rustc_1_28)]
+use core::ops::{Bound, RangeBounds};
+
 /// An iterator over the range [start, stop)
 #[derive(Clone)]
 pub struct Range<A> {
@@ -250,17 +253,6 @@ pub struct RangeStep<A> {
     rev: bool,
 }
 
-#[cfg(rustc_1_28)]
-impl<A> RangeBounds<A> for RangeStep<A> {
-    fn start_bound(&self) -> Bound<&A> {
-        Bound::Included(&self.state)
-    }
-
-    fn end_bound(&self) -> Bound<&A> {
-        Bound::Excluded(&self.stop)
-    }
-}
-
 /// Return an iterator over the range [start, stop) by `step`. It handles overflow by stopping.
 #[inline]
 pub fn range_step<A>(start: A, stop: A, step: A) -> RangeStep<A>
@@ -323,17 +315,6 @@ where
     }
 }
 
-#[cfg(rustc_1_28)]
-impl<A> RangeBounds<A> for RangeStepInclusive<A> {
-    fn start_bound(&self) -> Bound<&A> {
-        Bound::Included(&self.state)
-    }
-
-    fn end_bound(&self) -> Bound<&A> {
-        Bound::Included(&self.stop)
-    }
-}
-
 impl<A> Iterator for RangeStepInclusive<A>
 where
     A: CheckedAdd + PartialOrd + Clone + PartialEq,
@@ -435,17 +416,6 @@ where
     }
 }
 
-#[cfg(rustc_1_28)]
-impl<A> RangeBounds<A> for RangeStepFrom<A> {
-    fn start_bound(&self) -> Bound<&A> {
-        Bound::Included(&self.state)
-    }
-
-    fn end_bound(&self) -> Bound<&A> {
-        Bound::Unbounded
-    }
-}
-
 impl<A> Iterator for RangeStepFrom<A>
 where
     A: Add<A, Output = A> + Clone,