diff --git a/libc/include/signal.h b/libc/include/signal.h
index f1849c5..e23e65b 100644
--- a/libc/include/signal.h
+++ b/libc/include/signal.h
@@ -48,6 +48,9 @@
 #  include <linux/signal.h>
 #endif
 
+#include <sys/ucontext.h>
+#define __BIONIC_HAVE_UCONTEXT_T
+
 __BEGIN_DECLS
 
 typedef int sig_atomic_t;
diff --git a/libc/include/sys/ucontext.h b/libc/include/sys/ucontext.h
index f62380d..b8d4d58 100644
--- a/libc/include/sys/ucontext.h
+++ b/libc/include/sys/ucontext.h
@@ -68,11 +68,9 @@
   struct ucontext* uc_link;
   stack_t uc_stack;
   mcontext_t uc_mcontext;
+  sigset_t uc_sigmask;
   // Android has a wrong (smaller) sigset_t on ARM.
-  union {
-    sigset_t bionic;
-    uint32_t kernel[2];
-  } uc_sigmask;
+  uint32_t __padding_rt_sigset;
   // The kernel adds extra padding after uc_sigmask to match glibc sigset_t on ARM.
   char __padding[120];
   unsigned long uc_regspace[128] __attribute__((__aligned__(8)));
@@ -152,11 +150,9 @@
   struct ucontext* uc_link;
   stack_t uc_stack;
   mcontext_t uc_mcontext;
+  sigset_t uc_sigmask;
   // Android has a wrong (smaller) sigset_t on x86.
-  union {
-    sigset_t bionic;
-    uint32_t kernel[2];
-  } uc_sigmask;
+  uint32_t __padding_rt_sigset;
   struct _libc_fpstate __fpregs_mem;
 } ucontext_t;