diff --git a/libc/include/sys/procfs.h b/libc/include/sys/procfs.h
index 75a1e98..a082e97 100644
--- a/libc/include/sys/procfs.h
+++ b/libc/include/sys/procfs.h
@@ -26,16 +26,24 @@
  * SUCH DAMAGE.
  */
 
-#ifndef _SYS_PROCFS_H_
-#define _SYS_PROCFS_H_
+#pragma once
 
 #include <sys/cdefs.h>
+#include <sys/ptrace.h>
 #include <sys/ucontext.h>
 
 __BEGIN_DECLS
 
+#if defined(__arm__)
+#define ELF_NGREG (sizeof(struct user_regs) / sizeof(elf_greg_t))
+#elif defined(__aarch64__)
+#define ELF_NGREG (sizeof(struct user_pt_regs) / sizeof(elf_greg_t))
+#else
+#define ELF_NGREG (sizeof(struct user_regs_struct) / sizeof(elf_greg_t))
+#endif
+
 typedef unsigned long elf_greg_t;
-typedef elf_greg_t elf_gregset_t[NGREG];
+typedef elf_greg_t elf_gregset_t[ELF_NGREG];
 
 typedef fpregset_t elf_fpregset_t;
 
@@ -58,5 +66,3 @@
 #define ELF_PRARGSZ 80
 
 __END_DECLS
-
-#endif