diff --git a/src/type.zig b/src/type.zig
index 5685d097b9..9f954fb725 100644
--- a/src/type.zig
+++ b/src/type.zig
@@ -3619,6 +3619,9 @@ pub const Type = extern union {
 
             .@"struct" => {
                 if (sema_kit) |sk| _ = try sk.sema.resolveTypeFields(sk.block, sk.src, ty);
+                if (ty.containerLayout() != .Packed) {
+                    return (try ty.abiSizeAdvanced(target, if (sema_kit) |sk| .{ .sema_kit = sk } else .eager)).scalar * 8;
+                }
                 var total: u64 = 0;
                 for (ty.structFields().values()) |field| {
                     total += try bitSizeAdvanced(field.ty, target, sema_kit);
@@ -3628,6 +3631,9 @@ pub const Type = extern union {
 
             .tuple, .anon_struct => {
                 if (sema_kit) |sk| _ = try sk.sema.resolveTypeFields(sk.block, sk.src, ty);
+                if (ty.containerLayout() != .Packed) {
+                    return (try ty.abiSizeAdvanced(target, if (sema_kit) |sk| .{ .sema_kit = sk } else .eager)).scalar * 8;
+                }
                 var total: u64 = 0;
                 for (ty.tupleFields().types) |field_ty| {
                     total += try bitSizeAdvanced(field_ty, target, sema_kit);
@@ -3643,6 +3649,9 @@ pub const Type = extern union {
 
             .@"union", .union_safety_tagged, .union_tagged => {
                 if (sema_kit) |sk| _ = try sk.sema.resolveTypeFields(sk.block, sk.src, ty);
+                if (ty.containerLayout() != .Packed) {
+                    return (try ty.abiSizeAdvanced(target, if (sema_kit) |sk| .{ .sema_kit = sk } else .eager)).scalar * 8;
+                }
                 const union_obj = ty.cast(Payload.Union).?.data;
                 assert(union_obj.haveFieldTypes());
 
diff --git a/test/behavior/sizeof_and_typeof.zig b/test/behavior/sizeof_and_typeof.zig
index 45a99f9d32..01501b05b2 100644
--- a/test/behavior/sizeof_and_typeof.zig
+++ b/test/behavior/sizeof_and_typeof.zig
@@ -218,7 +218,7 @@ test "@bitSizeOf" {
     try expect(@bitSizeOf(u8) == @sizeOf(u8) * 8);
     try expect(@bitSizeOf(struct {
         a: u2,
-    }) == 2);
+    }) == 8);
     try expect(@bitSizeOf(packed struct {
         a: u2,
     }) == 2);