diff --git a/Code/GraphMol/Fingerprints/Wrap/MorganWrapper.cpp b/Code/GraphMol/Fingerprints/Wrap/MorganWrapper.cpp
index 8e0d5ba35..5bdbc9a9b 100644
--- a/Code/GraphMol/Fingerprints/Wrap/MorganWrapper.cpp
+++ b/Code/GraphMol/Fingerprints/Wrap/MorganWrapper.cpp
@@ -125,7 +125,7 @@ void exportMorgan() {
       python::return_value_policy<python::manage_new_object>());
 
   python::def("GetMorganAtomInvGen", &getMorganAtomInvGen,
-              (python::arg("includeRingMembership") = false),
+              (python::arg("includeRingMembership")),
               "Get a morgan atom invariants generator\n\n"
               "  ARGUMENTS:\n"
               "    - includeRingMembership: if set, whether or not the atom is "
diff --git a/Code/GraphMol/Fingerprints/Wrap/testGenerators.py b/Code/GraphMol/Fingerprints/Wrap/testGenerators.py
index 693c013f3..c996fc526 100644
--- a/Code/GraphMol/Fingerprints/Wrap/testGenerators.py
+++ b/Code/GraphMol/Fingerprints/Wrap/testGenerators.py
@@ -70,7 +70,7 @@ class TestCase(unittest.TestCase):
     nz = fp.GetNonzeroElements()
     self.assertEqual(len(nz), 14)
 
-    invgen = rdFingerprintGenerator.GetMorganAtomInvGen()
+    invgen = rdFingerprintGenerator.GetMorganAtomInvGen(True)
     g = rdFingerprintGenerator.GetMorganGenerator(radius=3, atomInvariantsGenerator=invgen)
     fp = g.GetSparseCountFingerprint(m)
     nz = fp.GetNonzeroElements()
diff --git a/ReleaseNotes.md b/ReleaseNotes.md
index 1a7f8ac7c..dd31c0185 100644
--- a/ReleaseNotes.md
+++ b/ReleaseNotes.md
@@ -23,6 +23,8 @@ Stephen, yuri@FreeBSD
   atom ranks.
 - 2D coordinate generation may produce different results for some molecules due
   to a change in the way the atom ordering is computed in the depiction code.
+- The `includeRingMembership` argument to `GetMorganAtomInvGen()` is now mandatory.
+  Previously, the default value was False.
 - Default ET-version in `ForceFields::CrystalFF::getExperimentalTorsions()` is
   changed from 1 to 2.