diff --git a/.readthedocs.yml b/.readthedocs.yml
index f3a5e31c..cb68e005 100644
--- a/.readthedocs.yml
+++ b/.readthedocs.yml
@@ -14,5 +14,6 @@ python:
           - rtd
 
 sphinx:
+  configuration: docs/conf.py
   builder: html
   fail_on_warning: true
diff --git a/myst_parser/mdit_to_docutils/base.py b/myst_parser/mdit_to_docutils/base.py
index bdd15156..3778dd31 100644
--- a/myst_parser/mdit_to_docutils/base.py
+++ b/myst_parser/mdit_to_docutils/base.py
@@ -716,8 +716,9 @@ def render_fence(self, token: SyntaxTreeNode) -> None:
         if not name and self.sphinx_env is not None:
             # use the current highlight setting, via the ``highlight`` directive,
             # or ``highlight_language`` configuration.
-            name = self.sphinx_env.temp_data.get(
-                "highlight_language", self.sphinx_env.config.highlight_language
+            name = (
+                self.sphinx_env.temp_data.get("highlight_language")
+                or self.sphinx_env.config.highlight_language
             )
 
         lineno_start = 1
diff --git a/pyproject.toml b/pyproject.toml
index e72f84a8..e97dff7f 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -75,6 +75,7 @@ testing = [
     "pytest-regressions",
     "pytest-param-files~=0.6.0",
     "sphinx-pytest",
+    "pygments<2.19",  # TODO fix test regression with 2.19"
 ]
 testing-docutils = [
     "pygments",