diff --git a/src/operator.rs b/src/operator.rs
index e5c695009cfa..be05c2259957 100644
--- a/src/operator.rs
+++ b/src/operator.rs
@@ -142,8 +142,9 @@ impl<'a, 'mir, 'tcx> EvalContextExt<'tcx> for super::MiriEvalContext<'a, 'mir, '
                     // allocations sit right next to each other.  The C/C++ standards are
                     // somewhat fuzzy about this case, so I think for now this check is
                     // "good enough".
-                    self.memory().check_bounds_ptr(left, false)?;
-                    self.memory().check_bounds_ptr(right, false)?;
+                    // We require liveness, as dead allocations can of course overlap.
+                    self.memory().check_bounds_ptr(left, InboundsCheck::Live)?;
+                    self.memory().check_bounds_ptr(right, InboundsCheck::Live)?;
                     // Two live in-bounds pointers, we can compare across allocations
                     left == right
                 }
@@ -153,15 +154,17 @@ impl<'a, 'mir, 'tcx> EvalContextExt<'tcx> for super::MiriEvalContext<'a, 'mir, '
             (Scalar::Bits { bits, size }, Scalar::Ptr(ptr)) => {
                 assert_eq!(size as u64, self.pointer_size().bytes());
                 let bits = bits as u64;
-                let (alloc_size, alloc_align) = self.memory().get_size_and_align(ptr.alloc_id);
 
                 // Case I: Comparing with NULL
                 if bits == 0 {
                     // Test if the ptr is in-bounds. Then it cannot be NULL.
-                    if ptr.offset <= alloc_size {
+                    if self.memory().check_bounds_ptr(ptr, InboundsCheck::MaybeDead).is_ok() {
                         return Ok(false);
                     }
                 }
+
+                let (alloc_size, alloc_align) = self.memory().get_size_and_align(ptr.alloc_id);
+
                 // Case II: Alignment gives it away
                 if ptr.offset.bytes() % alloc_align.abi() == 0 {
                     // The offset maintains the allocation alignment, so we know `base+offset`
@@ -293,11 +296,11 @@ impl<'a, 'mir, 'tcx> EvalContextExt<'tcx> for super::MiriEvalContext<'a, 'mir, '
         let offset = offset.checked_mul(pointee_size).ok_or_else(|| EvalErrorKind::Overflow(mir::BinOp::Mul))?;
         // Now let's see what kind of pointer this is
         if let Scalar::Ptr(ptr) = ptr {
-            // Both old and new pointer must be in-bounds.
+            // Both old and new pointer must be in-bounds of a *live* allocation.
             // (Of the same allocation, but that part is trivial with our representation.)
-            self.memory().check_bounds_ptr(ptr, false)?;
+            self.memory().check_bounds_ptr(ptr, InboundsCheck::Live)?;
             let ptr = ptr.signed_offset(offset, self)?;
-            self.memory().check_bounds_ptr(ptr, false)?;
+            self.memory().check_bounds_ptr(ptr, InboundsCheck::Live)?;
             Ok(Scalar::Ptr(ptr))
         } else {
             // An integer pointer. They can only be offset by 0, and we pretend there
diff --git a/src/stacked_borrows.rs b/src/stacked_borrows.rs
index 0da130260df2..063a544baa65 100644
--- a/src/stacked_borrows.rs
+++ b/src/stacked_borrows.rs
@@ -5,7 +5,7 @@ use rustc::hir::{Mutability, MutMutable, MutImmutable};
 
 use crate::{
     EvalResult, EvalErrorKind, MiriEvalContext, HelpersEvalContextExt, Evaluator, MutValueVisitor,
-    MemoryKind, MiriMemoryKind, RangeMap, AllocId, Allocation, AllocationExtra,
+    MemoryKind, MiriMemoryKind, RangeMap, AllocId, Allocation, AllocationExtra, InboundsCheck,
     Pointer, MemPlace, Scalar, Immediate, ImmTy, PlaceTy, MPlaceTy,
 };
 
@@ -523,7 +523,7 @@ impl<'a, 'mir, 'tcx> EvalContextExt<'tcx> for MiriEvalContext<'a, 'mir, 'tcx> {
         }
 
         // Get the allocation
-        self.memory().check_bounds(ptr, size, false)?;
+        self.memory().check_bounds(ptr, size, InboundsCheck::Live)?;
         let alloc = self.memory().get(ptr.alloc_id).expect("We checked that the ptr is fine!");
         // If we got here, we do some checking, *but* we leave the tag unchanged.
         if let Borrow::Shr(Some(_)) = ptr.tag {
@@ -566,7 +566,7 @@ impl<'a, 'mir, 'tcx> EvalContextExt<'tcx> for MiriEvalContext<'a, 'mir, 'tcx> {
             ptr, place.layout.ty, new_bor);
 
         // Get the allocation.  It might not be mutable, so we cannot use `get_mut`.
-        self.memory().check_bounds(ptr, size, false)?;
+        self.memory().check_bounds(ptr, size, InboundsCheck::Live)?;
         let alloc = self.memory().get(ptr.alloc_id).expect("We checked that the ptr is fine!");
         // Update the stacks.
         if let Borrow::Shr(Some(_)) = new_bor {
diff --git a/tests/compile-fail-fullmir/out_of_bounds_ptr_1.rs b/tests/compile-fail-fullmir/out_of_bounds_ptr_1.rs
index 8dce7e578626..ce1c89a2a008 100644
--- a/tests/compile-fail-fullmir/out_of_bounds_ptr_1.rs
+++ b/tests/compile-fail-fullmir/out_of_bounds_ptr_1.rs
@@ -1,4 +1,4 @@
-// error-pattern: pointer computed at offset 5, outside bounds of allocation
+// error-pattern: must be in-bounds and live at offset 5, but is outside bounds of allocation
 fn main() {
     let v = [0i8; 4];
     let x = &v as *const i8;