diff --git a/Python/ceval.c b/Python/ceval.c
index 7b7fdf0..816973f 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -51,7 +51,7 @@
 /* Turn this on if your compiler chokes on the big switch: */
 /* #define CASE_TOO_BIG 1 */
 
-#ifdef DEBUG
+#ifdef Py_DEBUG
 /* For debugging the interpreter: */
 #define LLTRACE  1	/* Low-level trace feature */
 #define CHECKEXC 1	/* Double-check exception checking */
@@ -339,7 +339,7 @@
 #ifdef LLTRACE
 	int lltrace;
 #endif
-#if defined(DEBUG) || defined(LLTRACE)
+#if defined(Py_DEBUG) || defined(LLTRACE)
 	/* Make it easier to find out where we are with a debugger */
 	char *filename = getstringvalue(co->co_filename);
 #endif
@@ -602,7 +602,7 @@
 
 		/* Extract opcode and argument */
 
-#if defined(DEBUG) || defined(LLTRACE)
+#if defined(Py_DEBUG) || defined(LLTRACE)
 		f->f_lasti = INSTR_OFFSET();
 #endif
 		
diff --git a/Python/thread.c b/Python/thread.c
index 0e6d6ee..ad7dd5c 100644
--- a/Python/thread.c
+++ b/Python/thread.c
@@ -83,7 +83,7 @@
 #define _P2(v1,t1,v2,t2)	(v1,v2) t1; t2;
 #endif /* __STDC__ */
 
-#ifdef DEBUG
+#ifdef Py_DEBUG
 static int thread_debug = 0;
 #define dprintf(args)	((thread_debug & 1) && printf args)
 #define d2printf(args)	((thread_debug & 8) && printf args)
@@ -98,7 +98,7 @@
 
 void init_thread _P0()
 {
-#ifdef DEBUG
+#ifdef Py_DEBUG
 	char *p = getenv("THREADDEBUG");
 
 	if (p) {
@@ -107,7 +107,7 @@
 		else
 			thread_debug = 1;
 	}
-#endif /* DEBUG */
+#endif /* Py_DEBUG */
 	if (initialized)
 		return;
 	initialized = 1;
diff --git a/Python/thread_sgi.h b/Python/thread_sgi.h
index 2774e49..32b94f2 100644
--- a/Python/thread_sgi.h
+++ b/Python/thread_sgi.h
@@ -77,7 +77,7 @@
 	}
 	if (do_exit) {
 		d2printf(("exiting in exit_sig\n"));
-#ifdef DEBUG
+#ifdef Py_DEBUG
 		if ((thread_debug & 8) == 0)
 			thread_debug &= ~1; /* don't produce debug messages */
 #endif
@@ -140,12 +140,12 @@
 	if (usconfig(CONF_ARENATYPE, US_SHAREDONLY) < 0)
 		perror("usconfig - CONF_ARENATYPE");
 	usconfig(CONF_LOCKTYPE, US_DEBUG); /* XXX */
-#ifdef DEBUG
+#ifdef Py_DEBUG
 	if (thread_debug & 4)
 		usconfig(CONF_LOCKTYPE, US_DEBUGPLUS);
 	else if (thread_debug & 2)
 		usconfig(CONF_LOCKTYPE, US_DEBUG);
-#endif /* DEBUG */
+#endif /* Py_DEBUG */
 	if ((shared_arena = usinit(tmpnam(0))) == 0)
 		perror("usinit");
 #ifdef USE_DL