diff --git a/docs/rtd-pip-requirements b/docs/rtd-pip-requirements
index 8ec2c036..2254f8e6 100644
--- a/docs/rtd-pip-requirements
+++ b/docs/rtd-pip-requirements
@@ -1,7 +1,9 @@
 stsci_rtd_theme
-numpy
+numpy >= 1.13
 matplotlib
 Cython
 astropy-helpers
 astropy
+sphinx-astropy
 sphinx_issues
+nbsphinx
diff --git a/poppy/optics.py b/poppy/optics.py
index 45d634b5..4072e1ad 100644
--- a/poppy/optics.py
+++ b/poppy/optics.py
@@ -10,7 +10,6 @@
 from . import utils
 from . import conf
 from . import accel_math
-from .version import version
 from .poppy_core import OpticalElement, Wavefront, BaseWavefront, PlaneType, _RADIANStoARCSEC
 from .accel_math import _exp, _r, _float, _complex
 from . import geometry
@@ -244,6 +243,10 @@ def to_fits(self, outname=None, what='amplitude', wavelength=1e-6 * u.meter, npi
         See the sample() function for additional optional parameters.
 
         """
+        try:
+            from .version import version
+        except ImportError:
+            version = ''
 
         kwargs['return_scale'] = True
 
diff --git a/readthedocs.yml b/readthedocs.yml
deleted file mode 100644
index 872c5627..00000000
--- a/readthedocs.yml
+++ /dev/null
@@ -1,7 +0,0 @@
-conda:
-    file: .rtd-environment.yml
-python:
-    setup_py_install: true
-    version: 3
-formats:
-    - pdf