diff --git a/src/block.zig b/src/block.zig
index bd4b17d..4d43262 100644
--- a/src/block.zig
+++ b/src/block.zig
@@ -4,6 +4,7 @@ const assert = std.debug.assert;
 const Allocator = std.mem.Allocator;
 const objc = @import("main.zig");
 
+extern "c" fn ghostty_arm64e_prepare_block(*anyopaque) void;
 // We have to use the raw C allocator for all heap allocation in here
 // because the objc runtime expects `malloc` to be used. If you don't use
 // malloc you'll get segfaults because the objc runtime will try to free
@@ -42,7 +43,7 @@ pub fn Block(
         const Self = @This();
         const captures_info = @typeInfo(Captures).@"struct";
         const InvokeFn = FnType(anyopaque);
-        const descriptor: Descriptor = .{
+        var descriptor: Descriptor = .{
             .reserved = 0,
             .size = @sizeOf(Context),
             .copy_helper = &descCopyHelper,
@@ -90,6 +91,7 @@ pub fn Block(
                 @field(ctx, field.name) = @field(captures, field.name);
             }
 
+            ghostty_arm64e_prepare_block(@ptrCast(&ctx));
             return ctx;
         }
 
diff --git a/src/class.zig b/src/class.zig
index e0c989c..697fe31 100644
--- a/src/class.zig
+++ b/src/class.zig
@@ -7,5 +7,7 @@ const objc = @import("main.zig");
 const MsgSend = @import("msg_send.zig").MsgSend;
 
+extern "c" fn ghostty_arm64e_sign_function(*const anyopaque) *const anyopaque;
+
 pub const Class = struct {
     value: c.Class,
 
@@ -65,7 +67,12 @@ pub const Class = struct {
         assert(fn_info.params.len >= 2);
         assert(fn_info.params[0].type == c.id);
         assert(fn_info.params[1].type == c.SEL);
-        _ = c.class_replaceMethod(self.value, objc.sel(name).value, @ptrCast(&imp), null);
+        _ = c.class_replaceMethod(
+            self.value,
+            objc.sel(name).value,
+            @ptrCast(@alignCast(ghostty_arm64e_sign_function(@ptrCast(&imp)))),
+            null,
+        );
     }
 
     // allows adding new methods; returns true on success.
@@ -81,7 +88,7 @@ pub const Class = struct {
         return boolResult(c.class_addMethod(
             self.value,
             objc.sel(name).value,
-            @ptrCast(&imp),
+            @ptrCast(@alignCast(ghostty_arm64e_sign_function(@ptrCast(&imp)))),
             &encoding,
         ));
     }