diff --git a/cpp.mk b/cpp.mk
index c133c635..6e8962cc 100644
--- a/cpp.mk
+++ b/cpp.mk
@@ -10,7 +10,7 @@ CPP_FLAGS_LOW=-march=i386 -m32 -fno-strict-aliasing -fno-pic -fno-toplevel-reord
 
 CPP_FLAGS_16=$(COMMON_CPP_FLAGS) $(CPP_FLAGS_LOW) -mregparm=3 -mpreferred-stack-boundary=2
 CPP_FLAGS_32=$(COMMON_CPP_FLAGS) $(CPP_FLAGS_LOW) -mpreferred-stack-boundary=4
-CPP_FLAGS_64=$(COMMON_CPP_FLAGS) -mno-sse -mno-sse2 -mno-sse3 -mno-sse4 -mno-sse4.1 -mno-sse4.2 -mno-avx
+CPP_FLAGS_64=$(COMMON_CPP_FLAGS) -mpreferred-stack-boundary=4 -mno-sse -mno-sse2 -mno-sse3 -mno-sse4 -mno-sse4.1 -mno-sse4.2 -mno-avx
 
 COMMON_LINK_FLAGS=-lgcc