diff --git a/.travis.yml b/.travis.yml
index 33aca913f07bd3608ab87381865bcc4fb35d110d..a981ea2544538cc96de76b958daf9fbeb25d7c82 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -4,8 +4,11 @@ python:
   - 3.6
 
 install: 
-  - pip install --user sphinx # sphinx_rtd_theme
-  - sudo python -m pip install https://github.com/rtfd/sphinx_rtd_theme/archive/master.zip -U
+  - pip install --user sphinx  # sphinx_rtd_theme
+    # pypi's sphinx_rtd_theme is outdated. Internet recommends using current
+    # master. Note: at some point, it will be OK to add `sphinx_rtd_theme` to
+    # the `pip install` above => remove line below:
+  - python -m pip install --user https://github.com/rtfd/sphinx_rtd_theme/archive/master.zip -U
 
 script: bash ./build_and_deploy.sh
 
diff --git a/docs/source/_static/theme_overrides.css b/docs/source/_static/theme_overrides.css
index 8623553e4aa36f24df9c894e3eeddc7af0331e37..db92babc73e090e6fd1ee73203f6b74493522c83 100644
--- a/docs/source/_static/theme_overrides.css
+++ b/docs/source/_static/theme_overrides.css
@@ -9,6 +9,9 @@
     overflow: visible;
 }
 
+/* rtd_theme currently colours code-blocks in the pygments style (ie. green).
+ * This overrides this design choice with white. Note: future versions of the
+ * sphinx_rtd_theme might not need this HACK. */
 .highlight {
     background: #ffffff;
 }