1 files changed, 1 insertions, 0 deletions
diff --git a/absl/copts/copts.py b/absl/copts/copts.py
index 704ef234..7c3edb64 100644
--- a/absl/copts/copts.py
+++ b/absl/copts/copts.py
@@ -128,6 +128,7 @@ COPT_VARS = {
         "-Wmissing-declarations",
         "-Woverlength-strings",
         "-Wpointer-arith",
+        "-Wundef",
         "-Wunused-local-typedefs",
         "-Wunused-result",
         "-Wvarargs",