diff --git a/README.md b/README.md
index 85c8190..8d8e583 100644
--- a/README.md
+++ b/README.md
@@ -246,6 +246,7 @@
 
 ### Debugging tips
 1. Key error for a new codename in libc/libc.map.txt
+
 e.g. what you add in libc/libc.map.txt is:
 
 ```
@@ -271,6 +272,7 @@
 Solution: Ask in the team and wait for the update.
 
 2. Use of undeclared identifier of the new system call in the test
+
 Possible Solution: Check everything ready in the files mentioned above first.
 Maybe glibc matters. Follow the example and try #if defined(__GLIBC__).
 
@@ -323,7 +325,7 @@
 
 Note that we use our own custom gtest runner that offers a superset of the
 options documented at
-<https://github.com/google/googletest/blob/master/googletest/docs/AdvancedGuide.md#running-test-programs-advanced-options>,
+<https://github.com/google/googletest/blob/main/docs/advanced.md#running-test-programs-advanced-options>,
 in particular for test isolation and parallelism (both on by default).
 
 ### Device tests via CTS
diff --git a/libc/include/sys/ucontext.h b/libc/include/sys/ucontext.h
index 72b8adb..8e5873d 100644
--- a/libc/include/sys/ucontext.h
+++ b/libc/include/sys/ucontext.h
@@ -366,7 +366,10 @@
   unsigned long uc_flags;
   struct ucontext_t* uc_link;
   stack_t uc_stack;
-  sigset_t uc_sigmask;
+  union {
+    sigset_t uc_sigmask;
+    sigset64_t uc_sigmask64;
+  };
   /* The kernel adds extra padding here to allow sigset_t to grow. */
   char __padding[128 - sizeof(sigset_t)];
   mcontext_t uc_mcontext;
diff --git a/libc/tools/gensyscalls.py b/libc/tools/gensyscalls.py
index d3e6ef4..a525a98 100755
--- a/libc/tools/gensyscalls.py
+++ b/libc/tools/gensyscalls.py
@@ -333,10 +333,12 @@
 class SysCallsTxtParser:
     def __init__(self):
         self.syscalls = []
-        self.lineno   = 0
+        self.lineno = 0
+        self.errors = False
 
     def E(self, msg):
         print("%d: %s" % (self.lineno, msg))
+        self.errors = True
 
     def parse_line(self, line):
         """ parse a syscall spec line.
@@ -443,6 +445,8 @@
             if not line: continue
             if line[0] == '#': continue
             self.parse_line(line)
+        if self.errors:
+            sys.exit(1)
 
     def parse_file(self, file_path):
         with open(file_path) as fp: