diff --git a/src/twisted/internet/_glibbase.py b/src/twisted/internet/_glibbase.py
index 8686e3cf2e7..4fc5271e75b 100644
--- a/src/twisted/internet/_glibbase.py
+++ b/src/twisted/internet/_glibbase.py
@@ -354,8 +354,8 @@ def simulate(self):
         if self._simtag is not None:
             self._source_remove(self._simtag)
         self.iterate()
-        timeout = min(self.timeout(), 0.01)
-        if timeout is None:
+        timeout = self.timeout()
+        if timeout is None or timeout > 0.01:
             timeout = 0.01
         self._simtag = self._timeout_add(
             int(timeout * 1000),
diff --git a/src/twisted/internet/test/test_glibbase.py b/src/twisted/internet/test/test_glibbase.py
index b391d47e4c8..b6b14b8bfaa 100644
--- a/src/twisted/internet/test/test_glibbase.py
+++ b/src/twisted/internet/test/test_glibbase.py
@@ -65,3 +65,36 @@ def test_ensureFailsWhenImported(self):
         )
         self.assertEqual(modules, {"m2": module})
         self.assertEqual(e.args, ("A message.",))
+
+
+try:
+    from twisted.internet import gireactor as _gireactor
+except ImportError:
+    gireactor = None
+else:
+    gireactor = _gireactor
+
+missingGlibReactor = None
+if gireactor is None:
+    missingGlibReactor = "gi reactor not available"
+
+
+class GlibReactorBaseTests(TestCase):
+    """
+    Tests for the private C{twisted.internet._glibbase.GlibReactorBase}
+    done via the public C{twisted.internet.gireactor.PortableGIReactor}
+    """
+
+    skip = missingGlibReactor
+
+    def test_simulate(self):
+        """
+        C{simulate} can be called without raising any errors when there are
+        no delayed calls for the reactor and hence there is no defined sleep
+        period.
+        """
+        sut = gireactor.PortableGIReactor(usegtk=False)
+        # Double check that reactor has no sleep period.
+        self.assertIs(None, sut.timeout())
+
+        sut.simulate()
diff --git a/src/twisted/newsfragments/9660.bugfix b/src/twisted/newsfragments/9660.bugfix
new file mode 100644
index 00000000000..f5d56197ea7
--- /dev/null
+++ b/src/twisted/newsfragments/9660.bugfix
@@ -0,0 +1 @@
+twisted.internet.glibbase.simulate no longer raises TypeError with no timeout on Python 3.
\ No newline at end of file