diff --git a/var/spack/repos/builtin/packages/cmake/package.py b/var/spack/repos/builtin/packages/cmake/package.py
index ea6b7c3a1b..298f629364 100644
--- a/var/spack/repos/builtin/packages/cmake/package.py
+++ b/var/spack/repos/builtin/packages/cmake/package.py
@@ -230,8 +230,6 @@ def flag_handler(self, name, flags):
     def bootstrap_args(self):
         spec = self.spec
         args = [
-            'CFLAGS=-O3',
-            'CXXFLAGS=-O3',
             '--prefix={0}'.format(self.prefix),
             '--parallel={0}'.format(make_jobs)
         ]