diff --git a/puzzles.h b/puzzles.h
index 0bdb581..09848d7 100644
--- a/puzzles.h
+++ b/puzzles.h
@@ -122,7 +122,8 @@ struct config_item {
  * Platform routines
  */
 
-#ifdef DEBUG
+/* We can't use #ifdef DEBUG, because Cygwin defines it by default. */
+#ifdef DEBUGGING
 #define debug(x) (debug_printf x)
 void debug_printf(char *fmt, ...);
 #else
diff --git a/windows.c b/windows.c
index 0cf8148..67469b1 100644
--- a/windows.c
+++ b/windows.c
@@ -33,7 +33,7 @@
 #define HELP_FILE_NAME  "puzzles.hlp"
 #define HELP_CNT_NAME   "puzzles.cnt"
 
-#ifdef DEBUG
+#ifdef DEBUGGING
 static FILE *debug_fp = NULL;
 static HANDLE debug_hdl = INVALID_HANDLE_VALUE;
 static int debug_got_console = 0;