diff --git a/vpython b/vpython
index 42d112fa7..55fd4aadc 100755
--- a/vpython
+++ b/vpython
@@ -42,11 +42,15 @@ export DEPOT_TOOLS_UNAME_S="${DEPOT_TOOLS_UNAME_S:-$(uname -s | tr '[:upper:]' '
 source "${DEPOT_TOOLS_DIR}/cipd_bin_setup.sh"
 cipd_bin_setup &> /dev/null
 
+# Don't pass this to the Python script as it might turn around and run commands
+# in other depot_tools dirs.
+base_dir="${DEPOT_TOOLS_DIR}"
+unset DEPOT_TOOLS_DIR
 case "${DEPOT_TOOLS_UNAME_S}" in
 mingw*|cygwin*)
   cmd.exe //c $0.bat "$@"
   ;;
 *)
-  exec "${DEPOT_TOOLS_DIR}/.cipd_bin/vpython" "$@"
+  exec "${base_dir}/.cipd_bin/vpython" "$@"
   ;;
 esac
diff --git a/vpython3 b/vpython3
index 3f2373dd3..1ff7a2520 100755
--- a/vpython3
+++ b/vpython3
@@ -40,11 +40,15 @@ export DEPOT_TOOLS_UNAME_S="${DEPOT_TOOLS_UNAME_S:-$(uname -s | tr '[:upper:]' '
 source "${DEPOT_TOOLS_DIR}/cipd_bin_setup.sh"
 cipd_bin_setup &> /dev/null
 
+# Don't pass this to the Python script as it might turn around and run commands
+# in other depot_tools dirs.
+base_dir="${DEPOT_TOOLS_DIR}"
+unset DEPOT_TOOLS_DIR
 case "${DEPOT_TOOLS_UNAME_S}" in
 mingw*|cygwin*)
   cmd.exe //c $0.bat "$@"
   ;;
 *)
-  exec "${DEPOT_TOOLS_DIR}/.cipd_bin/vpython3" "$@"
+  exec "${base_dir}/.cipd_bin/vpython3" "$@"
   ;;
 esac