diff --git a/var/spack/repos/builtin/packages/py-awkward/package.py b/var/spack/repos/builtin/packages/py-awkward/package.py
index 3a9ad343c2c..623f0168973 100644
--- a/var/spack/repos/builtin/packages/py-awkward/package.py
+++ b/var/spack/repos/builtin/packages/py-awkward/package.py
@@ -26,6 +26,7 @@ class PyAwkward(PythonPackage):
     patch('pybind11_02.patch', when="@1.2.3:")
 
     depends_on('py-setuptools', type='build')
+    depends_on('py-pyyaml', type='build')
 
     depends_on('python@2.7:2.8,3.5:', type=('build', 'run'))
     depends_on('py-numpy@1.13.1:', type=('build', 'run'))