diff --git a/lib/std/c/openbsd.zig b/lib/std/c/openbsd.zig
index 8bdd3125f5..341426ce62 100644
--- a/lib/std/c/openbsd.zig
+++ b/lib/std/c/openbsd.zig
@@ -1092,44 +1092,57 @@ comptime {
 }
 
 pub usingnamespace switch (builtin.cpu.arch) {
-    .x86_64 => struct {
-        pub const ucontext_t = extern struct {
-            sc_rdi: c_long,
-            sc_rsi: c_long,
-            sc_rdx: c_long,
-            sc_rcx: c_long,
-            sc_r8: c_long,
-            sc_r9: c_long,
-            sc_r10: c_long,
-            sc_r11: c_long,
-            sc_r12: c_long,
-            sc_r13: c_long,
-            sc_r14: c_long,
-            sc_r15: c_long,
-            sc_rbp: c_long,
-            sc_rbx: c_long,
-            sc_rax: c_long,
-            sc_gs: c_long,
-            sc_fs: c_long,
-            sc_es: c_long,
-            sc_ds: c_long,
-            sc_trapno: c_long,
-            sc_err: c_long,
-            sc_rip: c_long,
-            sc_cs: c_long,
-            sc_rflags: c_long,
-            sc_rsp: c_long,
-            sc_ss: c_long,
-
-            sc_fpstate: *anyopaque, // struct fxsave64 *
-            __sc_unused: c_int,
-            sc_mask: c_int,
-            sc_cookie: c_long,
-        };
-    },
+    .x86_64 => struct {},
     else => struct {},
 };
 
+pub const ucontext_t = switch (builtin.cpu.arch) {
+    .x86_64 => extern struct {
+        sc_rdi: c_long,
+        sc_rsi: c_long,
+        sc_rdx: c_long,
+        sc_rcx: c_long,
+        sc_r8: c_long,
+        sc_r9: c_long,
+        sc_r10: c_long,
+        sc_r11: c_long,
+        sc_r12: c_long,
+        sc_r13: c_long,
+        sc_r14: c_long,
+        sc_r15: c_long,
+        sc_rbp: c_long,
+        sc_rbx: c_long,
+        sc_rax: c_long,
+        sc_gs: c_long,
+        sc_fs: c_long,
+        sc_es: c_long,
+        sc_ds: c_long,
+        sc_trapno: c_long,
+        sc_err: c_long,
+        sc_rip: c_long,
+        sc_cs: c_long,
+        sc_rflags: c_long,
+        sc_rsp: c_long,
+        sc_ss: c_long,
+
+        sc_fpstate: *anyopaque, // struct fxsave64 *
+        __sc_unused: c_int,
+        sc_mask: c_int,
+        sc_cookie: c_long,
+    },
+    .aarch64 => extern struct {
+        __sc_unused: c_int,
+        sc_mask: c_int,
+        sc_sp: c_ulong,
+        sc_lr: c_ulong,
+        sc_elr: c_ulong,
+        sc_spsr: c_ulong,
+        sc_x: [30]c_ulong,
+        sc_cookie: c_long,
+    },
+    else => @compileError("missing ucontext_t type definition"),
+};
+
 pub const sigset_t = c_uint;
 pub const empty_sigset: sigset_t = 0;