diff --git a/clang/CMakeLists.txt b/clang/CMakeLists.txt
--- a/clang/CMakeLists.txt
+++ b/clang/CMakeLists.txt
@@ -256,7 +256,7 @@
 set(ENABLE_X86_RELAX_RELOCATIONS OFF CACHE BOOL
     "enable x86 relax relocations by default")
 
-set(ENABLE_EXPERIMENTAL_NEW_PASS_MANAGER FALSE CACHE BOOL
+set(ENABLE_EXPERIMENTAL_NEW_PASS_MANAGER TRUE CACHE BOOL
   "Enable the experimental new pass manager by default.")
 
 set(CLANG_SPAWN_CC1 OFF CACHE BOOL
diff --git a/llvm/utils/gn/secondary/clang/include/clang/Config/BUILD.gn b/llvm/utils/gn/secondary/clang/include/clang/Config/BUILD.gn
--- a/llvm/utils/gn/secondary/clang/include/clang/Config/BUILD.gn
+++ b/llvm/utils/gn/secondary/clang/include/clang/Config/BUILD.gn
@@ -34,7 +34,7 @@
     "BACKEND_PACKAGE_STRING=LLVM ${llvm_version}git",
     "ENABLE_LINKER_BUILD_ID=",
     "ENABLE_X86_RELAX_RELOCATIONS=",
-    "ENABLE_EXPERIMENTAL_NEW_PASS_MANAGER=",
+    "ENABLE_EXPERIMENTAL_NEW_PASS_MANAGER=1",
     "CLANG_ENABLE_OBJC_REWRITER=1",  # FIXME: flag?
     "CLANG_SYSTEMZ_DEFAULT_ARCH=z10",
   ]
diff --git a/llvm/utils/gn/secondary/clang/test/BUILD.gn b/llvm/utils/gn/secondary/clang/test/BUILD.gn
--- a/llvm/utils/gn/secondary/clang/test/BUILD.gn
+++ b/llvm/utils/gn/secondary/clang/test/BUILD.gn
@@ -57,7 +57,7 @@
     # builds exist, to make sure it's a toolchain var.
     "CMAKE_CXX_COMPILER=c++",
     "ENABLE_BACKTRACES=1",
-    "ENABLE_EXPERIMENTAL_NEW_PASS_MANAGER=0",
+    "ENABLE_EXPERIMENTAL_NEW_PASS_MANAGER=1",
     "LLVM_HOST_TRIPLE=$llvm_current_triple",
     "LLVM_LIT_TOOLS_DIR=",  # Intentionally empty, matches cmake build.
     "LLVM_USE_SANITIZER=",