--- a/memory/mozjemalloc/moz.build
+++ b/memory/mozjemalloc/moz.build
@@ -8,21 +8,16 @@ EXPORTS += [
     'mozjemalloc_types.h',
 ]
 
 SOURCES += [
     'mozjemalloc.cpp',
 ]
 FINAL_LIBRARY = 'memory'
 
-# See bug 422055.
-if CONFIG['OS_ARCH'] == 'SunOS' and not CONFIG['GNU_CC'] \
-        and CONFIG['MOZ_OPTIMIZE']:
-    CFLAGS += ['-xO5']
-
 DEFINES['MOZ_JEMALLOC_IMPL'] = True
 
 LOCAL_INCLUDES += [
     '/memory/build',
 ]
 
 if CONFIG['GNU_CXX']:
     # too many warnings from functions generated through rb_wrab from rb.h.