diff --git a/simgear/debug/debug_types.h b/simgear/debug/debug_types.h
index 9dfb88e2..d260cba0 100644
--- a/simgear/debug/debug_types.h
+++ b/simgear/debug/debug_types.h
@@ -23,7 +23,8 @@ typedef enum {
     SG_IO        = 0x00001000,
     SG_CLIPPER   = 0x00002000,
     SG_NETWORK   = 0x00004000,
-    SG_UNDEFD    = 0x00008000, // For range checking
+    SG_ATC       = 0x00008000,
+    SG_UNDEFD    = 0x00010000, // For range checking
 
     SG_ALL     = 0xFFFFFFFF
 } sgDebugClass;