diff --git a/libc/bionic/pthread_internal.h b/libc/bionic/pthread_internal.h
index 2151e03..3b91e6a 100644
--- a/libc/bionic/pthread_internal.h
+++ b/libc/bionic/pthread_internal.h
@@ -130,6 +130,9 @@
  */
 #define PTHREAD_STACK_SIZE_DEFAULT ((1 * 1024 * 1024) - SIGSTKSZ)
 
+/* Leave room for a guard page in the internally created signal stacks. */
+#define SIGNAL_STACK_SIZE (SIGSTKSZ + PAGE_SIZE)
+
 /* Needed by fork. */
 __LIBC_HIDDEN__ extern void __bionic_atfork_run_prepare();
 __LIBC_HIDDEN__ extern void __bionic_atfork_run_child();