diff --git a/build.py b/build.py
index 1f51748..8833486 100644
--- a/build.py
+++ b/build.py
@@ -55,8 +55,10 @@
     gpp_command.append('-flto=auto')
 
 if platform.system() == 'Darwin':
-    gpp_command.append('-L/usr/local/opt/llvm/lib')
     gpp_command.append('-Xpreprocessor')
+    gpp_command.append('-L/usr/local/opt/llvm/lib')
+    gpp_command.append('-O3')
+    gpp_command.remove('-Ofast')
 
 gpp_command += cpp_files + ['-o', OUTPUT_EXECUTABLE]
 nvcc_command = [