diff --git a/src/librustc_mir/interpret/eval_context.rs b/src/librustc_mir/interpret/eval_context.rs
index 1908f45704e..28dc0d37b36 100644
--- a/src/librustc_mir/interpret/eval_context.rs
+++ b/src/librustc_mir/interpret/eval_context.rs
@@ -775,7 +775,11 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpretCx<'mir, 'tcx, M> {
     }
 
     #[inline(always)]
-    pub fn force_bits(&self, scalar: Scalar<M::PointerTag>) -> InterpResult<'tcx, u128> {
-        self.memory.force_bits(scalar)
+    pub fn force_bits(
+        &self,
+        scalar: Scalar<M::PointerTag>,
+        size: Size
+    ) -> InterpResult<'tcx, u128> {
+        self.memory.force_bits(scalar, size)
     }
 }
diff --git a/src/librustc_mir/interpret/memory.rs b/src/librustc_mir/interpret/memory.rs
index fdea9b99da0..a0a34df3a5e 100644
--- a/src/librustc_mir/interpret/memory.rs
+++ b/src/librustc_mir/interpret/memory.rs
@@ -885,8 +885,12 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'mir, 'tcx, M> {
         }
     }
 
-    pub fn force_bits(&self, scalar: Scalar<M::PointerTag>) -> InterpResult<'tcx, u128> {
-        match scalar.to_bits_or_ptr(self.pointer_size(), self) {
+    pub fn force_bits(
+        &self,
+        scalar: Scalar<M::PointerTag>,
+        size: Size
+    ) -> InterpResult<'tcx, u128> {
+        match scalar.to_bits_or_ptr(size, self) {
             Ok(bits) => Ok(bits),
             Err(ptr) => Ok(M::ptr_to_int(ptr, &self.extra)? as u128)
         }
diff --git a/src/librustc_mir/interpret/operator.rs b/src/librustc_mir/interpret/operator.rs
index e8a69173379..029a440f34e 100644
--- a/src/librustc_mir/interpret/operator.rs
+++ b/src/librustc_mir/interpret/operator.rs
@@ -347,7 +347,7 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpretCx<'mir, 'tcx, M> {
             }
             _ => {
                 assert!(layout.ty.is_integral());
-                let val = val.to_bits(layout.size)?;
+                let val = self.force_bits(val, layout.size)?;
                 let res = match un_op {
                     Not => !val,
                     Neg => {
diff --git a/src/librustc_mir/interpret/place.rs b/src/librustc_mir/interpret/place.rs
index 7b8408f8808..a8f88af3f38 100644
--- a/src/librustc_mir/interpret/place.rs
+++ b/src/librustc_mir/interpret/place.rs
@@ -473,7 +473,7 @@ where
                 let layout = self.layout_of(self.tcx.types.usize)?;
                 let n = self.access_local(self.frame(), local, Some(layout))?;
                 let n = self.read_scalar(n)?;
-                let n = n.to_bits(self.tcx.data_layout.pointer_size)?;
+                let n = self.force_bits(n.not_undef()?, self.tcx.data_layout.pointer_size)?;
                 self.mplace_field(base, u64::try_from(n).unwrap())?
             }