Index: lib/Fuzzer/FuzzerInternal.h
===================================================================
--- lib/Fuzzer/FuzzerInternal.h
+++ lib/Fuzzer/FuzzerInternal.h
@@ -142,7 +142,7 @@
   size_t MaxMutationLen = 0;
 
   // Need to know our own thread.
-  static thread_local bool IsMyThread;
+  static __thread bool IsMyThread;
 };
 
 }; // namespace fuzzer
Index: lib/Fuzzer/FuzzerLoop.cpp
===================================================================
--- lib/Fuzzer/FuzzerLoop.cpp
+++ lib/Fuzzer/FuzzerLoop.cpp
@@ -41,7 +41,7 @@
 namespace fuzzer {
 static const size_t kMaxUnitSizeToPrint = 256;
 
-thread_local bool Fuzzer::IsMyThread;
+__thread bool Fuzzer::IsMyThread;
 
 SharedMemoryRegion SMR;