diff --git a/src/shims/unix/fs.rs b/src/shims/unix/fs.rs
index 40edd52c24..f8fefdddd3 100644
--- a/src/shims/unix/fs.rs
+++ b/src/shims/unix/fs.rs
@@ -1668,9 +1668,6 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
     fn chmod(&mut self, path_op: &OpTy<'tcx>, perm_op: &OpTy<'tcx>) -> InterpResult<'tcx, Scalar> {
         let this = self.eval_context_mut();
 
-        let pathname = this.read_path_from_c_str(this.read_pointer(path_op)?)?;
-        let perm = this.read_scalar(perm_op)?.to_uint(this.libc_ty_layout("mode_t").size)?;
-
         // Reject if isolation is enabled.
         if let IsolatedOp::Reject(reject_with) = this.machine.isolated_op {
             this.reject_in_isolation("`chmod`", reject_with)?;
@@ -1682,6 +1679,9 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
         {
             use std::os::unix::fs::PermissionsExt;
 
+            let pathname = this.read_path_from_c_str(this.read_pointer(path_op)?)?;
+            let perm = this.read_scalar(perm_op)?.to_uint(this.libc_ty_layout("mode_t").size)?;
+
             let result = std::fs::set_permissions(
                 pathname,
                 Permissions::from_mode(perm.try_into().unwrap()),
@@ -1699,20 +1699,21 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
     fn fchmod(&mut self, fd_op: &OpTy<'tcx>, perm_op: &OpTy<'tcx>) -> InterpResult<'tcx, Scalar> {
         let this = self.eval_context_mut();
 
-        let fd = this.read_scalar(fd_op)?.to_i32()?;
-        let perm = this.read_scalar(perm_op)?.to_uint(this.libc_ty_layout("mode_t").size)?;
-
         // Reject if isolation is enabled.
         if let IsolatedOp::Reject(reject_with) = this.machine.isolated_op {
             this.reject_in_isolation("`fchmod`", reject_with)?;
             // Set error code as "EBADF" (bad fd)
             return this.set_last_error_and_return_i32(LibcError("EBADF"));
         }
+        
         // `Permissions::from_mode` is Unix-specific.
         #[cfg(unix)]
         {
             use std::os::unix::fs::PermissionsExt;
 
+            let fd = this.read_scalar(fd_op)?.to_i32()?;
+            let perm = this.read_scalar(perm_op)?.to_uint(this.libc_ty_layout("mode_t").size)?;
+
             let Some(fd) = this.machine.fds.get(fd) else {
                 return this.set_last_error_and_return_i32(LibcError("EBADF"));
             };