diff --git a/src/sage/doctest/control.py b/src/sage/doctest/control.py
index 01f32fb8e4..4d83dc7b47 100644
--- a/src/sage/doctest/control.py
+++ b/src/sage/doctest/control.py
@@ -1253,6 +1253,7 @@ class DocTestController(SageObject):
 
             self.log("Using --optional=" + self._optional_tags_string())
             available_software._allow_external = self.options.optional is True or 'external' in self.options.optional
+            available_software._autodetect_safe = self.options.optional is True or 'sage' in self.options.optional
             self.log("Features to be detected: " + ','.join(available_software.detectable()))
             self.add_files()
             self.expand_files_into_sources()
diff --git a/src/sage/doctest/external.py b/src/sage/doctest/external.py
index 84dae19ea5..badc61466e 100644
--- a/src/sage/doctest/external.py
+++ b/src/sage/doctest/external.py
@@ -409,6 +409,7 @@ class AvailableSoftware(object):
             []
         """
         self._allow_external = True
+        self._autodetect_safe = True
         # For multiprocessing of doctests, the data self._seen should be
         # shared among subprocesses. Thus we use Array class from the
         # multiprocessing module.
@@ -430,6 +431,8 @@ class AvailableSoftware(object):
             sage: 'internet' in available_software # random, optional - internet
             True
         """
+        if not self._autodetect_safe:
+            return False
         try:
             idx = self._indices[item]
         except KeyError:
diff --git a/src/sage/features/sagemath.py b/src/sage/features/sagemath.py
index 433338766d..233623b14a 100644
--- a/src/sage/features/sagemath.py
+++ b/src/sage/features/sagemath.py
@@ -12,7 +12,7 @@ class sagemath_doc_html(StaticFile):
 
     EXAMPLES::
 
-        sage: from sage.features.sagemath import sagemath_doc_html
+        sage: from sage.features.sagemath import sagemath_doc_html  # optional - sagemath_doc_html
         sage: sagemath_doc_html().is_present()  # optional - sagemath_doc_html
         FeatureTestResult('sagemath_doc_html', True)
     """