diff --git a/doc/index.rst b/doc/index.rst
index 610f7cdb..3cbb266c 100644
--- a/doc/index.rst
+++ b/doc/index.rst
@@ -350,6 +350,10 @@ The following global options are defined. Note that all are typically formatted
      - :python:`"sympy.simplify(expr)"`
      - string
      - For all expressions ``expr`` that are rewritten internally: the contents of this parameter string are evaluated with ``eval()`` in Python to obtain the final output expression. Override for custom expression simplification steps. Example: ``"sympy.logcombine(sympy.powsimp(sympy.expand(expr)))"``.
+   * - ``forbidden_names``
+     - :python:`["oo", "zoo", "nan", "NaN", "__h"]`
+     - list of strings
+     - For each forbidden name: emit an error if a variable or parameter by this name occurs in the input.
 
 
 Output