diff --git a/build/fbcode_builder/getdeps/builder.py b/build/fbcode_builder/getdeps/builder.py
index 97a4d63d0..bc6c93965 100644
--- a/build/fbcode_builder/getdeps/builder.py
+++ b/build/fbcode_builder/getdeps/builder.py
@@ -12,17 +12,20 @@ import shutil
 import stat
 import subprocess
 import sys
+import typing
 
 from .dyndeps import create_dyn_dep_munger
 from .envfuncs import add_path_entry, Env, path_search
 from .fetcher import copy_if_different
 from .runcmd import run_cmd
 
+if typing.TYPE_CHECKING:
+    from .buildopts import BuildOptions
 
 class BuilderBase(object):
     def __init__(
         self,
-        build_opts,
+        build_opts: "BuildOptions",
         ctx,
         manifest,
         src_dir,
diff --git a/build/fbcode_builder/getdeps/buildopts.py b/build/fbcode_builder/getdeps/buildopts.py
index 108ddc9e2..de76a9525 100644
--- a/build/fbcode_builder/getdeps/buildopts.py
+++ b/build/fbcode_builder/getdeps/buildopts.py
@@ -83,7 +83,7 @@ class BuildOptions(object):
         # If we are running from an fbsource repository, set self.fbsource_dir
         # to allow the ShipIt-based fetchers to use it.
         if self.repo_project == "fbsource":
-            self.fbsource_dir = self.repo_root
+            self.fbsource_dir: Optional[str] = self.repo_root
         else:
             self.fbsource_dir = None
 
diff --git a/build/fbcode_builder/getdeps/cargo.py b/build/fbcode_builder/getdeps/cargo.py
index 574c471db..a594145af 100644
--- a/build/fbcode_builder/getdeps/cargo.py
+++ b/build/fbcode_builder/getdeps/cargo.py
@@ -7,14 +7,18 @@
 import os
 import re
 import shutil
+import typing
 
 from .builder import BuilderBase
 
+if typing.TYPE_CHECKING:
+    from .buildopts import BuildOptions
+
 
 class CargoBuilder(BuilderBase):
     def __init__(
         self,
-        build_opts,
+        build_opts: "BuildOptions",
         ctx,
         manifest,
         src_dir,
@@ -110,15 +114,16 @@ directory = "{vendored_dir}"
 """
                     )
 
-        # Point to vendored crates.io if possible
-        try:
-            from .facebook.rust import vendored_crates
+        if self.build_opts.fbsource_dir:
+            # Point to vendored crates.io if possible
+            try:
+                from .facebook.rust import vendored_crates
 
-            vendored_crates(self.build_opts, cargo_config_file)
-        except ImportError:
-            # This FB internal module isn't shippped to github,
-            # so just rely on cargo downloading crates on it's own
-            pass
+                vendored_crates(self.build_opts.fbsource_dir, cargo_config_file)
+            except ImportError:
+                # This FB internal module isn't shippped to github,
+                # so just rely on cargo downloading crates on it's own
+                pass
 
         return dep_to_git