diff --git a/src/user.zig b/src/user.zig
index 371460a..91f6b70 100644
--- a/src/user.zig
+++ b/src/user.zig
@@ -171,6 +171,7 @@ pub const PackedUser = struct {
             .gecos_len = gecos_len,
         };
         const innerBytes = mem.asBytes(&inner);
+
         var pos: usize = buf.*.len;
         buf.*.len += InnerSize +
             user.home.len +
@@ -207,9 +208,9 @@ pub const PackedUser = struct {
     pub fn maxSize() usize {
         comptime {
             const unpadded = InnerSize +
-                std.math.maxInt(u6) + // home
-                std.math.maxInt(u5) + // name
-                std.math.maxInt(u6) + // shell
+                std.math.maxInt(u6) + 1 + // home
+                std.math.maxInt(u5) + 1 + // name
+                std.math.maxInt(u6) + 1 + // shell
                 std.math.maxInt(u8); // gecos
             return pad.roundUp(u64, AlignmentBits, unpadded);
         }
@@ -323,7 +324,7 @@ test "construct PackedUser section" {
         .name = "Name" ** 8,
         .gecos = "Gecos" ** 51,
         .home = "Home" ** 16,
-        .shell = "She.l..l" ** 8,
+        .shell = "She.LllL" ** 8,
     }, User{
         .uid = 1002,
         .gid = 1002,
@@ -349,3 +350,19 @@ test "construct PackedUser section" {
     }
     try testing.expectEqual(users.len, i);
 }
+
+test "PackedUser.maxSize()" {
+    var buf = try ArrayList(u8).initCapacity(testing.allocator, PackedUser.maxSize());
+    defer buf.deinit();
+
+    const largeUser = User{
+        .uid = math.maxInt(u32),
+        .gid = math.maxInt(u32),
+        .name = "Name" ** 8, // 32
+        .gecos = "Gecos" ** 51, // 255
+        .home = "Home" ** 16, // 64
+        .shell = "She.LllL" ** 8, // 64
+    };
+    try PackedUser.packTo(&buf.items, largeUser, testShellIndex);
+    try testing.expectEqual(PackedUser.maxSize(), buf.items.len);
+}