diff --git a/Source/doomdef.h b/Source/doomdef.h
index b01464df..f2c834a7 100644
--- a/Source/doomdef.h
+++ b/Source/doomdef.h
@@ -30,6 +30,10 @@
 #ifndef __DOOMDEF__
 #define __DOOMDEF__
 
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
 // This must come first, since it redefines malloc(), free(), etc. -- killough:
 #include "z_zone.h"