diff --git a/make.h b/make.h
index d42720a9..f533e52c 100644
--- a/make.h
+++ b/make.h
@@ -306,7 +306,7 @@ extern unsigned int *reading_lineno_ptr;
 extern int just_print_flag, silent_flag, ignore_errors_flag, keep_going_flag;
 extern int debug_flag, print_data_base_flag, question_flag, touch_flag;
 extern int env_overrides, no_builtin_rules_flag, print_version_flag;
-extern int print_directory_flag;
+extern int print_directory_flag, warn_undefined_variables_flag;
 
 extern unsigned int job_slots;
 extern double max_load_average;