diff --git a/mozilla/gc/boehm/macbuild/MacOS_config.h b/mozilla/gc/boehm/macbuild/MacOS_config.h
index e5dd273ad87..0e8ce9ef917 100644
--- a/mozilla/gc/boehm/macbuild/MacOS_config.h
+++ b/mozilla/gc/boehm/macbuild/MacOS_config.h
@@ -33,6 +33,7 @@
 #define NO_SIGNALS				// signals aren't real on the Macintosh.
 #define USE_TEMPORARY_MEMORY	// use Macintosh temporary memory.
 #define FIND_LEAK				// use as a leak detector.
+#define LARGE_CONFIG			// try a big heap, for fun.
 
 // CFLAGS= -O -DNO_SIGNALS -DSILENT -DALL_INTERIOR_POINTERS
 //