diff --git a/compiler-rt/lib/tsan/rtl/tsan_dispatch_defs.h b/compiler-rt/lib/tsan/rtl/tsan_dispatch_defs.h
--- a/compiler-rt/lib/tsan/rtl/tsan_dispatch_defs.h
+++ b/compiler-rt/lib/tsan/rtl/tsan_dispatch_defs.h
@@ -51,11 +51,18 @@
 #define DISPATCH_DATA_DESTRUCTOR_MUNMAP  _dispatch_data_destructor_munmap
 
 #if __has_attribute(noescape)
-  #define DISPATCH_NOESCAPE __attribute__((__noescape__))
+# define DISPATCH_NOESCAPE __attribute__((__noescape__))
 #else
-  #define DISPATCH_NOESCAPE
+# define DISPATCH_NOESCAPE
 #endif
 
+#if SANITIZER_MAC
+# define SANITIZER_WEAK_IMPORT extern "C" __attribute((weak_import))
+#else
+# define SANITIZER_WEAK_IMPORT extern "C" __attribute((weak))
+#endif
+
+
 // Data types used in dispatch APIs
 typedef unsigned long size_t;
 typedef unsigned long uintptr_t;
diff --git a/compiler-rt/lib/tsan/rtl/tsan_interceptors_libdispatch.cpp b/compiler-rt/lib/tsan/rtl/tsan_interceptors_libdispatch.cpp
--- a/compiler-rt/lib/tsan/rtl/tsan_interceptors_libdispatch.cpp
+++ b/compiler-rt/lib/tsan/rtl/tsan_interceptors_libdispatch.cpp
@@ -219,8 +219,19 @@
 DISPATCH_INTERCEPT(dispatch, false)
 DISPATCH_INTERCEPT(dispatch_barrier, true)
 
-DISPATCH_INTERCEPT_SYNC_F(dispatch_async_and_wait_f, false)
+// dispatch_async_and_wait[_f] was introduced in macOS 10.14, which is greater
+// than our minimal deployment target.  We need to forward declare it as a "weak
+// import" to ensure we generate a weak reference so the TSan dylib continues to
+// work on older systems.  We cannot simply #include <dispatch.h> or use the
+// Darwin availability macros since this file is multi-platform.
+SANITIZER_WEAK_IMPORT void dispatch_async_and_wait(
+    dispatch_queue_t queue, DISPATCH_NOESCAPE dispatch_block_t block);
+SANITIZER_WEAK_IMPORT void dispatch_async_and_wait_f(
+    dispatch_queue_t queue, void *context, dispatch_function_t work);
+
 DISPATCH_INTERCEPT_SYNC_B(dispatch_async_and_wait, false)
+DISPATCH_INTERCEPT_SYNC_F(dispatch_async_and_wait_f, false)
+
 
 DECLARE_REAL(void, dispatch_after_f, dispatch_time_t when,
              dispatch_queue_t queue, void *context, dispatch_function_t work)