diff --git a/ndk/platforms/android-21/include/sys/ucontext.h b/ndk/platforms/android-21/include/sys/ucontext.h
index 399458ebe..9e3c6530d 100644
--- a/ndk/platforms/android-21/include/sys/ucontext.h
+++ b/ndk/platforms/android-21/include/sys/ucontext.h
@@ -82,12 +82,6 @@ typedef struct ucontext {
 #define NGREG 34 /* x0..x30 + sp + pc + pstate */
 typedef unsigned long greg_t;
 typedef greg_t gregset_t[NGREG];
-
-struct user_fpsimd_struct {
-  long double vregs[32];
-  uint32_t fpsr;
-  uint32_t fpcr;
-};
 typedef struct user_fpsimd_struct fpregset_t;
 
 #include <asm/sigcontext.h>
diff --git a/ndk/platforms/android-21/include/sys/user.h b/ndk/platforms/android-21/include/sys/user.h
index d63fe6aa5..3312981d3 100644
--- a/ndk/platforms/android-21/include/sys/user.h
+++ b/ndk/platforms/android-21/include/sys/user.h
@@ -30,11 +30,13 @@
 #define _SYS_USER_H_
 
 #include <sys/cdefs.h>
-#include <limits.h> /* For PAGE_SIZE. */
 #include <stddef.h> /* For size_t. */
 
 __BEGIN_DECLS
 
+#define PAGE_SIZE 4096
+#define PAGE_MASK (~(PAGE_SIZE - 1))
+
 #if __i386__
 
 struct user_fpregs_struct {
@@ -230,7 +232,17 @@ struct user {
 
 #elif defined(__aarch64__)
 
-// There are no user structures for 64 bit arm.
+struct user_regs_struct {
+  uint64_t regs[31];
+  uint64_t sp;
+  uint64_t pc;
+  uint64_t pstate;
+};
+struct user_fpsimd_struct {
+  __uint128_t vregs[32];
+  uint32_t fpsr;
+  uint32_t fpcr;
+};
 
 #else