diff --git a/Mac/mwerks/mwerks_applet_config.h b/Mac/mwerks/mwerks_applet_config.h
index 3e54034dfda..fc332f80d06 100644
--- a/Mac/mwerks/mwerks_applet_config.h
+++ b/Mac/mwerks/mwerks_applet_config.h
@@ -19,14 +19,19 @@
 #define MAC_TCL			/* This *must* be on if USE_TK is on */
 /* #define USE_MAC_SHARED_LIBRARY	/* Enable code to add shared-library resources */
 #define USE_MAC_APPLET_SUPPORT	/* Enable code to run a PYC resource */
-/* #define USE_MAC_DYNAMIC_LOADING		/* Enable dynamically loaded modules */
 /* #define USE_MALLOC_DEBUG			/* Enable range checking and other malloc debugging */
 #define USE_GDBM		/* Include the gdbm module */
 #define USE_ZLIB		/* Include the zlib module */
 #define USE_APPEARANCE	/* Enable Appearance support */
+
+#define USE_MSL_MALLOC	/* Disable private malloc. Also disables next two defines */
+#ifndef USE_MSL_MALLOC
+/* #define USE_MALLOC_DEBUG			/* Enable range checking and other malloc debugging */
 #ifdef __powerc
 #define USE_CACHE_ALIGNED 8		/* Align on 32-byte boundaries for 604 */
 #endif
+#endif
+
 #ifdef USE_MSL
 #define MSL_USE_PRECOMPILED_HEADERS 0	/* Don't use precomp headers: we include our own */
 #include <ansi_prefix.mac.h>
diff --git a/Mac/mwerks/mwerks_carbon_config.h b/Mac/mwerks/mwerks_carbon_config.h
index b39467e302b..e886d369764 100644
--- a/Mac/mwerks/mwerks_carbon_config.h
+++ b/Mac/mwerks/mwerks_carbon_config.h
@@ -27,15 +27,19 @@
 /* #define USE_MAC_SHARED_LIBRARY	/* Enable code to add shared-library resources */
 /* #define USE_MAC_APPLET_SUPPORT	/* Enable code to run a PYC resource */
 /* #define HAVE_DYNAMIC_LOADING		/* Enable dynamically loaded modules */
-/* #define USE_MALLOC_DEBUG			/* Enable range checking and other malloc debugging */
 /* #define USE_GDBM		/* Include the gdbm module */
 /* #define USE_ZLIB		/* Include the zlib module */
 #define USE_UCNHASH		/* Include ucnhash module */
 #define USE_APPEARANCE	/* Enable Appearance support */
-#define USE_MSL_MALLOC	/* Use MSL malloc(), not our own. */
+
+#define USE_MSL_MALLOC	/* Disable private malloc. Also disables next two defines */
+#ifndef USE_MSL_MALLOC
+/* #define USE_MALLOC_DEBUG			/* Enable range checking and other malloc debugging */
 #ifdef __powerc
 #define USE_CACHE_ALIGNED 8		/* Align on 32-byte boundaries for 604 */
 #endif
+#endif
+
 #ifdef USE_MSL
 #define MSL_USE_PRECOMPILED_HEADERS 0	/* Don't use precomp headers: we include our own */
 #include <ansi_prefix.mac.h>
diff --git a/Mac/mwerks/mwerks_nonshared_config.h b/Mac/mwerks/mwerks_nonshared_config.h
index acae953364a..797d52619b1 100644
--- a/Mac/mwerks/mwerks_nonshared_config.h
+++ b/Mac/mwerks/mwerks_nonshared_config.h
@@ -19,13 +19,18 @@
 /* #define USE_MAC_SHARED_LIBRARY	/* Enable code to add shared-library resources */
 /* #define USE_MAC_APPLET_SUPPORT	/* Enable code to run a PYC resource */
 /* #define HAVE_DYNAMIC_LOADING		/* Enable dynamically loaded modules */
-/* #define USE_MALLOC_DEBUG			/* Enable range checking and other malloc debugging */
 #define USE_GDBM		/* Include the gdbm module */
 #define USE_ZLIB		/* Include the zlib module */
 #define USE_APPEARANCE	/* Enable Appearance support */
+
+#define USE_MSL_MALLOC	/* Disable private malloc. Also disables next two defines */
+#ifndef USE_MSL_MALLOC
+/* #define USE_MALLOC_DEBUG			/* Enable range checking and other malloc debugging */
 #ifdef __powerc
 #define USE_CACHE_ALIGNED 8		/* Align on 32-byte boundaries for 604 */
 #endif
+#endif
+
 #ifdef USE_MSL
 #define MSL_USE_PRECOMPILED_HEADERS 0	/* Don't use precomp headers: we include our own */
 #include <ansi_prefix.mac.h>
diff --git a/Mac/mwerks/mwerks_shared_config.h b/Mac/mwerks/mwerks_shared_config.h
index 67cc9d7f0ba..36272a478a0 100644
--- a/Mac/mwerks/mwerks_shared_config.h
+++ b/Mac/mwerks/mwerks_shared_config.h
@@ -24,13 +24,18 @@
 #define USE_MAC_SHARED_LIBRARY		/* Enable code to add shared-library resources */
 #define USE_MAC_APPLET_SUPPORT		/* Enable code to run a PYC resource */
 #define HAVE_DYNAMIC_LOADING		/* Enable dynamically loaded modules */
-/* #define USE_MALLOC_DEBUG			/* Enable range checking and other malloc debugging */
 /* #define USE_GDBM		/* Include the gdbm module */
 /* #define USE_ZLIB		/* Include the zlib module */
 #define USE_APPEARANCE	/* Enable Appearance support */
+
+#define USE_MSL_MALLOC	/* Disable private malloc. Also disables next two defines */
+#ifndef USE_MSL_MALLOC
+/* #define USE_MALLOC_DEBUG			/* Enable range checking and other malloc debugging */
 #ifdef __powerc
 #define USE_CACHE_ALIGNED 8		/* Align on 32-byte boundaries for 604 */
 #endif
+#endif
+
 #ifdef USE_MSL
 #define MSL_USE_PRECOMPILED_HEADERS 0	/* Don't use precomp headers: we include our own */
 #include <ansi_prefix.mac.h>
diff --git a/Mac/mwerks/mwerks_small_config.h b/Mac/mwerks/mwerks_small_config.h
index 5b99aa5dbec..53554138cc4 100644
--- a/Mac/mwerks/mwerks_small_config.h
+++ b/Mac/mwerks/mwerks_small_config.h
@@ -21,14 +21,19 @@
 /* #define USE_MAC_SHARED_LIBRARY	/* Enable code to add shared-library resources */
 /* #define USE_MAC_APPLET_SUPPORT	/* Enable code to run a PYC resource */
 /* #define HAVE_DYNAMIC_LOADING		/* Enable dynamically loaded modules */
-/* #define USE_MALLOC_DEBUG			/* Enable range checking and other malloc debugging */
 /* #define USE_GDBM		/* Include the gdbm module */
 /* #define USE_ZLIB		/* Include the zlib module */
 #define USE_UCNHASH	/* Include the ucnhash module */
 #define USE_APPEARANCE	/* Enable Appearance support */
+
+#define USE_MSL_MALLOC	/* Disable private malloc. Also disables next two defines */
+#ifndef USE_MSL_MALLOC
+/* #define USE_MALLOC_DEBUG			/* Enable range checking and other malloc debugging */
 #ifdef __powerc
 #define USE_CACHE_ALIGNED 8		/* Align on 32-byte boundaries for 604 */
 #endif
+#endif
+
 #ifdef USE_MSL
 #define MSL_USE_PRECOMPILED_HEADERS 0	/* Don't use precomp headers: we include our own */
 #include <ansi_prefix.mac.h>
diff --git a/Mac/mwerks/mwerks_threadsmall_config.h b/Mac/mwerks/mwerks_threadsmall_config.h
index 70a11a0ab5c..223039eb218 100644
--- a/Mac/mwerks/mwerks_threadsmall_config.h
+++ b/Mac/mwerks/mwerks_threadsmall_config.h
@@ -22,13 +22,18 @@
 /* #define USE_MAC_SHARED_LIBRARY	/* Enable code to add shared-library resources */
 /* #define USE_MAC_APPLET_SUPPORT	/* Enable code to run a PYC resource */
 /* #define HAVE_DYNAMIC_LOADING		/* Enable dynamically loaded modules */
-#define USE_MALLOC_DEBUG			/* Enable range checking and other malloc debugging */
 /* #define USE_GDBM		/* Include the gdbm module */
 /* #define USE_ZLIB		/* Include the zlib module */
 #define USE_APPEARANCE	/* Enable Appearance support */
+
+#define USE_MSL_MALLOC	/* Disable private malloc. Also disables next two defines */
+#ifndef USE_MSL_MALLOC
+/* #define USE_MALLOC_DEBUG			/* Enable range checking and other malloc debugging */
 #ifdef __powerc
 #define USE_CACHE_ALIGNED 8		/* Align on 32-byte boundaries for 604 */
 #endif
+#endif
+
 #ifdef USE_MSL
 #define MSL_USE_PRECOMPILED_HEADERS 0	/* Don't use precomp headers: we include our own */
 #include <ansi_prefix.mac.h>