diff --git a/docs/source/_ext/lexers.py b/docs/source/_ext/lexers.py
index 41f492c..4ade9f2 100644
--- a/docs/source/_ext/lexers.py
+++ b/docs/source/_ext/lexers.py
@@ -405,6 +405,7 @@ class CustomPythonLexer(MixinLexer, PythonLexer):
             "dict",
             "dir",
             "divmod",
+            "double",  # added
             "enumerate",
             "eval",
             "execfile",