diff --git a/bootstrap/manifest.txt b/bootstrap/manifest.txt
index 7b0f8b2f56..28bca33c11 100644
--- a/bootstrap/manifest.txt
+++ b/bootstrap/manifest.txt
@@ -15,13 +15,16 @@
 # the string "cpython3/" and ends with the CIPD tag "version:VERSION".
 # It uses this to extract VERSION.
 
-$VerifiedPlatform windows-386 windows-amd64 linux-amd64 mac-amd64
+$VerifiedPlatform windows-amd64 linux-amd64 mac-amd64
 
+# TODO(https://crbug.com/1184768): Remove `=amd64` once mac/arm64 python exists
 @Subdir python
-infra/3pp/tools/cpython/${platform} version:2.7.17.chromium.22
+infra/3pp/tools/cpython/${os}-${arch=amd64} version:2.7.17.chromium.22
 
+# TODO(https://crbug.com/1103326): Remove `=amd64` once mac/arm64 python3 exists
 @Subdir python3
-infra/3pp/tools/cpython3/${os}-${arch} version:3.8.0.chromium.8
+infra/3pp/tools/cpython3/${os}-${arch=amd64} version:3.8.0.chromium.8
 
+# TODO(https://crbug.com/1184766): Remove `=amd64` once mac/arm64 git exists
 @Subdir git
-infra/3pp/tools/git/${os}-${arch} version:2@2.30.2.chromium.6
+infra/3pp/tools/git/${os}-${arch=amd64} version:2@2.30.2.chromium.6
diff --git a/bootstrap_python3 b/bootstrap_python3
index 96110dee56..341c0e52e7 100644
--- a/bootstrap_python3
+++ b/bootstrap_python3
@@ -29,6 +29,11 @@ function bootstrap_python3 {
       -root "$BOOTSTRAP_PATH"
 
   BOOTSTRAP_PYTHON_BIN="${BOOTSTRAP_PATH}/python3/bin/python3"
+  if [[ ! -x "$BOOTSTRAP_PYTHON_BIN" && $(uname -sm) == "Darwin arm64" ]]; then
+    # There's no CIPD python3 package on mac/arm64. fall back to system python3.
+    # TODO(https://crbug.com/1103326): Remove once mac/arm64 python3 exists.
+    BOOTSTRAP_PYTHON_BIN=python3
+  fi
   "$BOOTSTRAP_PYTHON_BIN" "bootstrap/bootstrap.py" --bootstrap-name "$BOOTSTRAP_PATH"
 
   cd - > /dev/null