diff --git a/update_depot_tools b/update_depot_tools
index 8ce17216b1..eb7343e2ad 100755
--- a/update_depot_tools
+++ b/update_depot_tools
@@ -119,7 +119,9 @@ function update_git_repo {
 }
 
 # Update git checkouts.
-if [ "X$DEPOT_TOOLS_UPDATE" != "X0" ]; then
+if [ "X$DEPOT_TOOLS_UPDATE" = "X0" ]; then
+  echo "DEPOT_TOOLS_UPDATE environment variable is 0, skipping update. Set DEPOT_TOOLS_UPDATE to 1 to force update." >&2
+else
   if [ -e "$base_dir/.git" ]; then
     cd "$base_dir"
     update_git_repo