diff --git a/src/librustc_mir/const_eval.rs b/src/librustc_mir/const_eval.rs
index 74df2898db4..10dbe1799a5 100644
--- a/src/librustc_mir/const_eval.rs
+++ b/src/librustc_mir/const_eval.rs
@@ -372,7 +372,7 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
     }
 
     fn call_extra_fn(
-        _ecx: &mut InterpretCx<'mir, 'tcx, Self>,
+        _ecx: &mut InterpCx<'mir, 'tcx, Self>,
         fn_val: !,
         _args: &[OpTy<'tcx>],
         _dest: Option<PlaceTy<'tcx>>,
diff --git a/src/librustc_mir/interpret/machine.rs b/src/librustc_mir/interpret/machine.rs
index b35d468c49a..5d88274eb96 100644
--- a/src/librustc_mir/interpret/machine.rs
+++ b/src/librustc_mir/interpret/machine.rs
@@ -127,7 +127,7 @@ pub trait Machine<'mir, 'tcx>: Sized {
     /// Execute `fn_val`.  it is the hook's responsibility to advance the instruction
     /// pointer as appropriate.
     fn call_extra_fn(
-        ecx: &mut InterpretCx<'mir, 'tcx, Self>,
+        ecx: &mut InterpCx<'mir, 'tcx, Self>,
         fn_val: Self::ExtraFnVal,
         args: &[OpTy<'tcx, Self::PointerTag>],
         dest: Option<PlaceTy<'tcx, Self::PointerTag>>,
diff --git a/src/librustc_mir/interpret/validity.rs b/src/librustc_mir/interpret/validity.rs
index 5049c50004a..642227fe29c 100644
--- a/src/librustc_mir/interpret/validity.rs
+++ b/src/librustc_mir/interpret/validity.rs
@@ -6,14 +6,12 @@ use rustc::hir;
 use rustc::ty::layout::{self, TyLayout, LayoutOf, VariantIdx};
 use rustc::ty;
 use rustc_data_structures::fx::FxHashSet;
-use rustc::mir::interpret::{
-    GlobalAlloc, InterpResult, InterpError,
-};
 
 use std::hash::Hash;
 
 use super::{
-    OpTy, Machine, InterpCx, ValueVisitor, MPlaceTy,
+    GlobalAlloc, InterpResult, InterpError,
+    OpTy, Machine, InterpCx, ValueVisitor, MPlaceTy, AllocCheck,
 };
 
 macro_rules! validation_failure {
@@ -505,19 +503,20 @@ impl<'rt, 'mir, 'tcx, M: Machine<'mir, 'tcx>> ValueVisitor<'mir, 'tcx, M>
                     // Only NULL is the niche.  So make sure the ptr is NOT NULL.
                     if self.ecx.memory.ptr_may_be_null(ptr) {
                         // These conditions are just here to improve the diagnostics so we can
-                        // differentiate between null pointers and dangling pointers
+                        // differentiate between null pointers and dangling pointers.
                         if self.ref_tracking_for_consts.is_some() &&
-                            self.ecx.memory.get(ptr.alloc_id).is_err() &&
-                            self.ecx.memory.get_fn(ptr.into()).is_err() {
+                            self.ecx.memory.get_size_and_align(ptr.alloc_id, AllocCheck::Live)
+                                .is_err()
+                        {
                             return validation_failure!(
-                                "encountered dangling pointer", self.path
+                                "a dangling pointer", self.path
                             );
                         }
                         return validation_failure!("a potentially NULL pointer", self.path);
                     }
                     return Ok(());
                 } else {
-                    // Conservatively, we reject, because the pointer *could* have this
+                    // Conservatively, we reject, because the pointer *could* have a bad
                     // value.
                     return validation_failure!(
                         "a pointer",