diff --git a/memory/mozjemalloc/jemalloc.c b/memory/mozjemalloc/jemalloc.c
index 07a39623ea..c842f23837 100644
--- a/memory/mozjemalloc/jemalloc.c
+++ b/memory/mozjemalloc/jemalloc.c
@@ -142,7 +142,7 @@
 /*
  * Uncomment this to use only one arena by default.
  */
-#define MOZ_MEMORY_NARENAS_DEFAULT_ONE
+// #define MOZ_MEMORY_NARENAS_DEFAULT_ONE
 
 /*
  * Pass this set of options to jemalloc as its default. It does not override