diff --git a/simgear/simgear_config_cmake.h.in b/simgear/simgear_config_cmake.h.in
index 34af5094..bb6d092b 100644
--- a/simgear/simgear_config_cmake.h.in
+++ b/simgear/simgear_config_cmake.h.in
@@ -21,4 +21,3 @@
 
 #cmakedefine SYSTEM_EXPAT
 #cmakedefine ENABLE_SOUND
-#cmakedefine SIMGEAR_HEADLESS