diff --git a/conf.py b/conf.py
index 7e35e3d376..efcd455e01 100644
--- a/conf.py
+++ b/conf.py
@@ -266,19 +266,9 @@ rst_epilog = """
 
 # -- Options for HTML output ----------------------------------------------
 
-# on_rtd is whether we are on readthedocs.org
-on_rtd = os.environ.get('READTHEDOCS', None) == 'True'
-
-if not on_rtd:  # only import and set the theme if we're building docs locally
-    try:
-        import sphinx_rtd_theme
-        html_theme = 'sphinx_rtd_theme'
-        html_theme_path = [sphinx_rtd_theme.get_html_theme_path(), '.']
-    except:
-        html_theme = 'default'
-        html_theme_path = ['.']
-else:
-    html_theme_path = ['.']
+import sphinx_rtd_theme
+html_theme = 'sphinx_rtd_theme'
+html_theme_path = [sphinx_rtd_theme.get_html_theme_path(), '.']
 
 # Theme options are theme-specific and customize the look and feel of a theme
 # further.  For a list of options available for each theme, see the
diff --git a/tools/ci_set_matrix.py b/tools/ci_set_matrix.py
index e3527bc90d..e5ac80c912 100755
--- a/tools/ci_set_matrix.py
+++ b/tools/ci_set_matrix.py
@@ -45,6 +45,7 @@ from shared_bindings_matrix import (
 # Files that never influence board builds
 IGNORE_BOARD = {
     ".devcontainer",
+    "conf.py",
     "docs",
     "tests",
     "tools/ci_changes_per_commit.py",