diff --git a/src/shell.zig b/src/shell.zig
index 0534d6d..d17c2b3 100644
--- a/src/shell.zig
+++ b/src/shell.zig
@@ -17,7 +17,7 @@ pub const ShellReader = struct {
 
     pub fn init(index: []const u8, blob: []const u8) ShellReader {
         return ShellReader{
-            .sectionIndex = @bitCast([]const ShellIndex, index),
+            .sectionIndex = std.mem.bytesAsSlice(ShellIndex, index),
             .sectionBlob = blob,
         };
     }
@@ -78,7 +78,7 @@ pub const ShellWriter = struct {
         }
 
         pub fn sectionIndex(self: *const ShellSections) []const u8 {
-            return @bitCast([]const u8, self.index.constSlice());
+            return std.mem.sliceAsBytes(self.index.constSlice());
         }
 
         pub fn sectionBlob(self: *const ShellSections) []const u8 {
@@ -176,7 +176,7 @@ inline fn roundUp4Padding(n: u12) u12 {
 // to 4 bytes.
 // The actual shell length is len+1: we don't allow empty shells, and the real
 // length of the shell is 1-64 bytes.
-const ShellIndex = struct {
+const ShellIndex = packed struct {
     offset: u10,
     len: u6,
 };