diff --git a/packages/py-nixio/package.py b/packages/py-nixio/package.py
index a6cb7b70d5d0e3baddea2e7377fb788c07b9fc47..5ee35af2fcecd4df9939a38977cdf8b5d823113d 100644
--- a/packages/py-nixio/package.py
+++ b/packages/py-nixio/package.py
@@ -20,5 +20,6 @@ class PyNixio(PythonPackage):
 
     depends_on("py-setuptools", type="build")
 
+    depends_on("py-six", type=("build", "run"))
     depends_on("py-numpy", type=("build", "run"))
     depends_on("py-h5py", type=("build", "run"))