diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_mac.cpp b/compiler-rt/lib/sanitizer_common/sanitizer_mac.cpp
index d4811ff4ed217..bf861063ca1f5 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_mac.cpp
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_mac.cpp
@@ -1298,6 +1298,29 @@ uptr FindAvailableMemoryRange(uptr size, uptr alignment, uptr left_padding,
   return 0;
 }
 
+// Returns true if the address is definitely mapped, and false if it is not
+// mapped or could not be determined.
+bool IsAddressInMappedRegion(uptr addr) {
+  mach_vm_size_t vmsize = 0;
+  natural_t depth = 0;
+  vm_region_submap_short_info_data_64_t vminfo;
+  mach_msg_type_number_t count = VM_REGION_SUBMAP_SHORT_INFO_COUNT_64;
+  mach_vm_address_t address = addr;
+
+  kern_return_t kr =
+      mach_vm_region_recurse(mach_task_self(), &address, &vmsize, &depth,
+                             (vm_region_info_t)&vminfo, &count);
+
+  if (kr == KERN_DENIED) {
+    Report(
+        "WARN: mach_vm_region_recurse returned KERN_DENIED when checking "
+        "whether an address is mapped.\n");
+    Report("HINT: Is mach_vm_region_recurse allowed by sandbox?\n");
+  }
+
+  return (kr == KERN_SUCCESS && addr >= address && addr < address + vmsize);
+}
+
 // FIXME implement on this platform.
 void GetMemoryProfile(fill_profile_f cb, uptr *stats) {}
 
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_mac.h b/compiler-rt/lib/sanitizer_common/sanitizer_mac.h
index b0e4ac7f40745..789dd8e4d8e9c 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_mac.h
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_mac.h
@@ -76,6 +76,8 @@ struct ThreadEventCallbacks {
 
 void InstallPthreadIntrospectionHook(const ThreadEventCallbacks &callbacks);
 
+bool IsAddressInMappedRegion(uptr addr);
+
 }  // namespace __sanitizer
 
 #endif  // SANITIZER_APPLE
diff --git a/compiler-rt/lib/tsan/rtl/tsan_platform_mac.cpp b/compiler-rt/lib/tsan/rtl/tsan_platform_mac.cpp
index eb344df168ab9..5cc81bab5b911 100644
--- a/compiler-rt/lib/tsan/rtl/tsan_platform_mac.cpp
+++ b/compiler-rt/lib/tsan/rtl/tsan_platform_mac.cpp
@@ -226,9 +226,19 @@ static void ThreadTerminateCallback(uptr thread) {
 void InitializePlatformEarly() {
 #  if !SANITIZER_GO && SANITIZER_IOS
   uptr max_vm = GetMaxUserVirtualAddress() + 1;
-  if (max_vm != HiAppMemEnd()) {
-    Printf("ThreadSanitizer: unsupported vm address limit %p, expected %p.\n",
-           (void *)max_vm, (void *)HiAppMemEnd());
+  if (max_vm < HiAppMemEnd()) {
+    Report(
+        "ThreadSanitizer: Unsupported virtual memory layout:\n\tVM address "
+        "limit = %p\n\tExpected %p.\n",
+        (void*)max_vm, (void*)HiAppMemEnd());
+    Die();
+  }
+  // In some configurations, the max_vm is expanded, but much of this space is
+  // already mapped. TSAN will not work in this configuration.
+  if (IsAddressInMappedRegion(HiAppMemEnd() - 1)) {
+    Report(
+        "ThreadSanitizer: Unsupported virtual memory layout: Address %p is "
+        "already mapped.\n");
     Die();
   }
 #endif