diff --git a/dtool/Config.Win32.pp b/dtool/Config.Win32.pp
index fc3b555e49..4661691d75 100644
--- a/dtool/Config.Win32.pp
+++ b/dtool/Config.Win32.pp
@@ -104,8 +104,8 @@
 // this indicates OLD_STYLE_ALLOCATOR is NOT used (defined as the empty string)
 #define OLD_STYLE_ALLOCATOR
 
-// this is reqd for msvc 7.0 to build (beta-only, havent tested final)
-// #define UNKNOWN_ALLOCATOR 1
+// this is reqd for msvc 7.0 to build (beta-only, havent tested final).  Default on for Opt4, off otherwise
+//#define USE_UNKNOWN_ALLOCATOR 1
 
 // can Intel C++ build this directory successfully (if not, change CC to msvc)
 #define NOT_INTEL_BUILDABLE false
diff --git a/dtool/LocalSetup.pp b/dtool/LocalSetup.pp
index 385143bc04..cae46222c1 100644
--- a/dtool/LocalSetup.pp
+++ b/dtool/LocalSetup.pp
@@ -191,7 +191,11 @@ $[cdefine HAVE_RTTI]
 $[cdefine GLOBAL_OPERATOR_NEW_EXCEPTIONS]
 
 /* What style STL allocator should we declare? */
-$[cdefine UNKNOWN_ALLOCATOR]
+
+// Use this to force UNKNOWN_ALLOCATOR for non-Opt4 (it is already default for Opt4 using /DUNKNOWN_ALLOCATOR)
+// see dtoolbase.h
+$[cdefine USE_UNKNOWN_ALLOCATOR]
+
 $[cdefine OLD_STYLE_ALLOCATOR]
 $[cdefine GNU_STYLE_ALLOCATOR]
 
diff --git a/dtool/src/dtoolbase/dtoolbase.h b/dtool/src/dtoolbase/dtoolbase.h
index 00bffa6895..a27b4cc8a5 100644
--- a/dtool/src/dtoolbase/dtoolbase.h
+++ b/dtool/src/dtoolbase/dtoolbase.h
@@ -58,6 +58,10 @@
 
 #endif  /* WIN32_VC */
 
+#if defined(USE_UNKNOWN_ALLOCATOR) && !defined(UNKNOWN_ALLOCATOR)
+#define UNKNOWN_ALLOCATOR 1
+#endif
+
 #include "dtoolsymbols.h"
 
 #ifdef HAVE_MALLOC_H