diff --git a/devtools/conda-envs/test_env.yaml b/devtools/conda-envs/test_env.yaml
index a136ba9..147bd15 100644
--- a/devtools/conda-envs/test_env.yaml
+++ b/devtools/conda-envs/test_env.yaml
@@ -17,6 +17,7 @@ dependencies:
   - wheel
   - pytest-pep8
   - build
+  - sphinx
 
     # Pip-only installs
   #- pip:
diff --git a/readthedocs.yml b/readthedocs.yml
index 0c9b025..e127ce4 100644
--- a/readthedocs.yml
+++ b/readthedocs.yml
@@ -8,10 +8,10 @@ formats:
   - pdf
 
 python:
-  version: 3.7
+  version: 3.9
   install:
     - method: pip
       path: .
 
 conda:
-    environment: environment.yml
\ No newline at end of file
+    environment: devtools/conda-envs/test_env.yaml
\ No newline at end of file