diff --git a/rust-version b/rust-version
index 3a7d316af8e9..538003d9fbae 100644
--- a/rust-version
+++ b/rust-version
@@ -1 +1 @@
-02046a5d402c789c006d0da7662f800fe3c45faf
+a5fb9ae5b2ed3cb011ada9dc1e8633aa0927f279
diff --git a/src/eval.rs b/src/eval.rs
index d2ca57c39a79..8274b52bd085 100644
--- a/src/eval.rs
+++ b/src/eval.rs
@@ -114,7 +114,7 @@ pub fn create_ecx<'mir, 'tcx: 'mir>(
             ecx.layout_of(tcx.mk_array(tcx.mk_imm_ptr(tcx.types.u8), u64::try_from(argvs.len()).unwrap()))?;
         let argvs_place = ecx.allocate(argvs_layout, MiriMemoryKind::Machine.into());
         for (idx, arg) in argvs.into_iter().enumerate() {
-            let place = ecx.mplace_field(argvs_place, u64::try_from(idx).unwrap())?;
+            let place = ecx.mplace_field(argvs_place, idx)?;
             ecx.write_scalar(arg, place.into())?;
         }
         ecx.memory.mark_immutable(argvs_place.ptr.assert_ptr().alloc_id)?;
@@ -154,7 +154,7 @@ pub fn create_ecx<'mir, 'tcx: 'mir>(
             // Store the UTF-16 string. We just allocated so we know the bounds are fine.
             let char_size = Size::from_bytes(2);
             for (idx, &c) in cmd_utf16.iter().enumerate() {
-                let place = ecx.mplace_field(cmd_place, u64::try_from(idx).unwrap())?;
+                let place = ecx.mplace_field(cmd_place, idx)?;
                 ecx.write_scalar(Scalar::from_uint(c, char_size), place.into())?;
             }
         }
diff --git a/src/helpers.rs b/src/helpers.rs
index 7ca2b238218a..11f95f40b909 100644
--- a/src/helpers.rs
+++ b/src/helpers.rs
@@ -598,7 +598,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
         // Store the UTF-16 string.
         let char_size = Size::from_bytes(2);
         for (idx, c) in u16_vec.into_iter().chain(iter::once(0x0000)).enumerate() {
-            let place = this.mplace_field(mplace, u64::try_from(idx).unwrap())?; 
+            let place = this.mplace_field(mplace, idx)?;
             this.write_scalar(Scalar::from_uint(c, char_size), place.into())?;
         }
         Ok((true, string_length))
diff --git a/src/shims/env.rs b/src/shims/env.rs
index 192fc0d47abe..34c297248f0d 100644
--- a/src/shims/env.rs
+++ b/src/shims/env.rs
@@ -61,7 +61,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
         Ok(match this.machine.env_vars.map.get(name) {
             // The offset is used to strip the "{name}=" part of the string.
             Some(var_ptr) => {
-                Scalar::from(var_ptr.offset(Size::from_bytes(u64::try_from(name.len()).unwrap().checked_add(1).unwrap()), this)?)
+                Scalar::from(var_ptr.offset(Size::from_bytes(name.len()) + Size::from_bytes(1), this)?)
             }
             None => Scalar::ptr_null(&*this.tcx),
         })
@@ -187,7 +187,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
             this.layout_of(tcx.mk_array(tcx.types.usize, u64::try_from(vars.len()).unwrap()))?;
         let vars_place = this.allocate(vars_layout, MiriMemoryKind::Machine.into());
         for (idx, var) in vars.into_iter().enumerate() {
-            let place = this.mplace_field(vars_place, u64::try_from(idx).unwrap())?;
+            let place = this.mplace_field(vars_place, idx)?;
             this.write_scalar(var, place.into())?;
         }
         this.write_scalar(