diff --git a/lib/Makefile.m32 b/lib/Makefile.m32
index 8c0e5a467..319678643 100644
--- a/lib/Makefile.m32
+++ b/lib/Makefile.m32
@@ -50,8 +50,16 @@ ifndef LIBCARES_PATH
 LIBCARES_PATH = ../ares
 endif
 
+# Edit the var below to set to your architecture or set environment var.
+ifndef ARCH
+ARCH = w32
+endif
+
 CC = gcc
 CFLAGS = -g -O2 -Wall
+ifeq ($(ARCH),w64)
+CFLAGS += -D_AMD64_
+endif
 # comment LDFLAGS below to keep debug info
 LDFLAGS = -s
 AR = ar
diff --git a/src/Makefile.m32 b/src/Makefile.m32
index 3cafae7bb..f0263237a 100644
--- a/src/Makefile.m32
+++ b/src/Makefile.m32
@@ -50,8 +50,16 @@ ifndef LIBCARES_PATH
 LIBCARES_PATH = ../ares
 endif
 
+# Edit the var below to set to your architecture or set environment var.
+ifndef ARCH
+ARCH = w32
+endif
+
 CC = gcc
 CFLAGS = -g -O2 -Wall
+ifeq ($(ARCH),w64)
+CFLAGS += -D_AMD64_
+endif
 # comment LDFLAGS below to keep debug info
 LDFLAGS = -s
 RC = windres