--- a/src/gcc/config/i386/t-gnu64
+++ b/src/gcc/config/i386/t-gnu64
@@ -36,3 +36,13 @@ MULTILIB_DIRNAMES   = $(patsubst m%, %,
 MULTILIB_OSDIRNAMES = m64=../lib64$(call if_multiarch,:x86_64-gnu)
 MULTILIB_OSDIRNAMES+= m32=$(if $(wildcard $(shell echo $(SYSTEM_HEADER_DIR))/../../usr/lib32),../lib32,../lib)$(call if_multiarch,:i386-gnu)
 MULTILIB_OSDIRNAMES+= mx32=../libx32$(call if_multiarch,:x86_64-gnux32)
+
+ifneq (,$(findstring x86_64,$(target)))
+  ifneq (,$(findstring biarchx32.h,$(tm_include_list)))
+  MULTIARCH_DIRNAME = $(call if_multiarch,x86_64-gnux32)
+  else
+  MULTIARCH_DIRNAME = $(call if_multiarch,x86_64-gnu)
+  endif
+else
+  MULTIARCH_DIRNAME = $(call if_multiarch,i386-gnu)
+endif