diff --git a/var/spack/repos/builtin/packages/nettle/package.py b/var/spack/repos/builtin/packages/nettle/package.py
index 841de42b2f..32f7c424e6 100644
--- a/var/spack/repos/builtin/packages/nettle/package.py
+++ b/var/spack/repos/builtin/packages/nettle/package.py
@@ -22,3 +22,6 @@ class Nettle(AutotoolsPackage):
 
     depends_on('gmp')
     depends_on('m4', type='build')
+
+    def configure_args(self):
+        return ['CFLAGS={0}'.format(self.compiler.c99_flag)]