diff --git a/compiler-rt/lib/dfsan/dfsan_custom.cpp b/compiler-rt/lib/dfsan/dfsan_custom.cpp
--- a/compiler-rt/lib/dfsan/dfsan_custom.cpp
+++ b/compiler-rt/lib/dfsan/dfsan_custom.cpp
@@ -756,6 +756,7 @@
   DFsanThread *t = (DFsanThread *)arg;
   SetCurrentThread(t);
   t->Init();
+  SetSigProcMask(&t->starting_sigset_, nullptr);
   return t->ThreadStart();
 }
 
@@ -776,6 +777,10 @@
   DFsanThread *t =
       DFsanThread::Create(start_routine_trampoline,
                           (thread_callback_t)start_routine, arg, track_origins);
+
+  ScopedBlockSignals block;
+  block.GetSavedSet(&t->starting_sigset_);
+
   int res = pthread_create(thread, attr, DFsanThreadStartFunc, t);
 
   if (attr == &myattr)
diff --git a/compiler-rt/lib/dfsan/dfsan_thread.h b/compiler-rt/lib/dfsan/dfsan_thread.h
--- a/compiler-rt/lib/dfsan/dfsan_thread.h
+++ b/compiler-rt/lib/dfsan/dfsan_thread.h
@@ -15,6 +15,7 @@
 
 #include "dfsan_allocator.h"
 #include "sanitizer_common/sanitizer_common.h"
+#include "sanitizer_common/sanitizer_posix.h"
 
 namespace __dfsan {
 
@@ -45,6 +46,7 @@
   DFsanThreadLocalMallocStorage &malloc_storage() { return malloc_storage_; }
 
   int destructor_iterations_;
+  __sanitizer_sigset_t starting_sigset_;
 
  private:
   void SetThreadStackAndTls();