diff --git a/lib/motion/project/builder.rb b/lib/motion/project/builder.rb
index 340427d3..255eaf72 100644
--- a/lib/motion/project/builder.rb
+++ b/lib/motion/project/builder.rb
@@ -88,7 +88,8 @@ module Motion; module Project;
             # LLVM bitcode.
             bc = File.join(objs_build_dir, "#{path}.#{arch}.bc")
             bs_flags = bs_files.map { |x| "--uses-bs \"" + x + "\" " }.join(' ')
-            sh "/usr/bin/env VM_KERNEL_PATH=\"#{kernel}\" VM_OPT_LEVEL=\"#{config.opt_level}\" /usr/bin/arch -arch #{arch} #{ruby} #{bs_flags} --emit-llvm \"#{bc}\" #{init_func} \"#{path}\""
+            arch_cmd = (arch =~ /^arm/) ? "/usr/bin/arch -arch i386" : "/usr/bin/arch -arch #{arch}"
+            sh "/usr/bin/env VM_KERNEL_PATH=\"#{kernel}\" VM_OPT_LEVEL=\"#{config.opt_level}\" #{arch_cmd} #{ruby} #{bs_flags} --emit-llvm \"#{bc}\" #{init_func} \"#{path}\""
    
             # Assembly.
             asm = File.join(objs_build_dir, "#{path}.#{arch}.s")