diff --git a/third_party/llvm-10.0/BUILD.gn b/third_party/llvm-10.0/BUILD.gn
index 583b7dd..8591921 100644
--- a/third_party/llvm-10.0/BUILD.gn
+++ b/third_party/llvm-10.0/BUILD.gn
@@ -894,6 +894,7 @@
     "llvm/lib/Support/Program.cpp",
     "llvm/lib/Support/RandomNumberGenerator.cpp",
     "llvm/lib/Support/Regex.cpp",
+    "llvm/lib/Support/RWMutex.cpp",
     "llvm/lib/Support/SHA1.cpp",
     "llvm/lib/Support/ScaledNumber.cpp",
     "llvm/lib/Support/ScopedPrinter.cpp",