diff --git a/tools/hxcpp/BuildTool.hx b/tools/hxcpp/BuildTool.hx
index 15339a9a9..b2e76b9d6 100644
--- a/tools/hxcpp/BuildTool.hx
+++ b/tools/hxcpp/BuildTool.hx
@@ -136,12 +136,20 @@ class BuildTool
       arm64 = mDefines.exists("HXCPP_ARM64");
       if (m64==m32 && !arm64)
       {
-         var arch = getArch();
+         var arch = mDefines.get("HXCPP_ARCH");
+         if (arch != null) {
+            m64 = arch == "x86_64";
+            m32 = arch == "x86";
+            arm64 = arch == "arm64";
+         } else {
+            var hostArch = getArch();
+
+            // Default to the current OS version.  windowsArm runs m32 code too
+            m64 = hostArch == "m64";
+            m32 = hostArch == "m32";
+            arm64 = hostArch == "arm64";
+         }
 
-         // Default to the current OS version.  windowsArm runs m32 code too
-         m64 = arch=="m64";
-         m32 = arch=="m32";
-         arm64 = arch=="arm64";
          mDefines.remove(m32 ? "HXCPP_M64" : "HXCPP_M32");
          set64(mDefines,m64,arm64);
       }