diff --git a/llvm/lib/Fuzzer/FuzzerDriver.cpp b/llvm/lib/Fuzzer/FuzzerDriver.cpp
index d432fe8..ab1fdf7 100644
--- a/llvm/lib/Fuzzer/FuzzerDriver.cpp
+++ b/llvm/lib/Fuzzer/FuzzerDriver.cpp
@@ -23,6 +23,7 @@
 #include <mutex>
 #include <string>
 #include <thread>
+#include <unistd.h>
 
 // This function should be present in the libFuzzer so that the client
 // binary can test for its existence.
@@ -441,7 +442,7 @@
   // Initialize Seed.
   if (Seed == 0)
     Seed = (std::chrono::system_clock::now().time_since_epoch().count() << 10) +
-           GetPid();
+           getpid();
   if (Flags.verbosity)
     Printf("INFO: Seed: %u\n", Seed);