diff --git a/pid/tuning.hpp b/pid/tuning.hpp
index ba4ec32..7f1cb63 100644
--- a/pid/tuning.hpp
+++ b/pid/tuning.hpp
@@ -11,3 +11,8 @@
 extern std::string loggingPath;
 /** Boolean variable whether loggingPath is non-empty. */
 extern bool loggingEnabled;
+
+/** Boolean variable controlling whether debug mode is enabled
+ * during this run.
+ */
+extern bool debugEnabled;