diff --git a/.bumpversion.cfg b/.bumpversion.cfg
index 42f48c05d..d14feddb5 100644
--- a/.bumpversion.cfg
+++ b/.bumpversion.cfg
@@ -1,5 +1,5 @@
 [bumpversion]
-current_version = 3.16.0
+current_version = 3.16.1
 commit = True
 tag = False
 parse = (?P<major>\d+)\.(?P<minor>\d+)\.(?P<release>[a-z]+)?(?P<patch>\d+)?
diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index 6e5f63187..ea40d73ab 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -1,3 +1,13 @@
+DIALS 3.16.1 (2023-08-29)
+=========================
+
+Bugfixes
+--------
+
+- Fix situation where a bad ``Beam.probe`` could cause undefined behaviour. (`#656 <https://github.com/cctbx/dxtbx/issues/656>`_)
+- Fix performance regression loading large experiment lists containing profile/scaling models. (`#658 <https://github.com/cctbx/dxtbx/issues/658>`_)
+
+
 dxtbx 3.16.0 (2023-08-14)
 =========================
 
diff --git a/setup.py b/setup.py
index 8d6f78679..0f9cdb4fa 100644
--- a/setup.py
+++ b/setup.py
@@ -8,7 +8,7 @@
 
 # Static version number which is updated by bump2version
 # Do not change this manually - use 'bump2version <major/minor/patch/release>'
-__version_tag__ = "3.16.0"
+__version_tag__ = "3.16.1"
 
 setup_kwargs = {
     "name": "dxtbx",
diff --git a/src/dxtbx/model/beam.h b/src/dxtbx/model/beam.h
index 6df5325d1..7f9cefb37 100644
--- a/src/dxtbx/model/beam.h
+++ b/src/dxtbx/model/beam.h
@@ -319,7 +319,7 @@ namespace dxtbx { namespace model {
       case neutron:
         return std::string("neutron");
       default:
-        DXTBX_ERROR("Unknown probe type");
+        throw DXTBX_ERROR("Unknown probe type");
       }
     }
 
@@ -335,7 +335,7 @@ namespace dxtbx { namespace model {
         return Probe::neutron;
       }
 
-      DXTBX_ERROR("Unknown probe " + probe);
+      throw DXTBX_ERROR("Unknown probe " + probe);
     }
 
     void set_probe(Probe probe) {
diff --git a/src/dxtbx/model/experiment_list.py b/src/dxtbx/model/experiment_list.py
index ec836614f..92298851d 100644
--- a/src/dxtbx/model/experiment_list.py
+++ b/src/dxtbx/model/experiment_list.py
@@ -64,6 +64,14 @@ class InvalidExperimentListError(RuntimeError):
     """
 
 
+try:
+    scaling_model_entry_points = importlib.metadata.entry_points()[
+        "dxtbx.scaling_model_ext"
+    ]
+except KeyError:
+    scaling_model_entry_points = []
+
+
 class ExperimentListDict:
     """A helper class for serializing the experiment list to dictionary (needed
     to save the experiment list to JSON format."""
@@ -465,7 +473,7 @@ def _lookup_model(self, name, experiment_dict):
     @staticmethod
     def _scaling_model_from_dict(obj):
         """Get the scaling model from a dictionary."""
-        for entry_point in importlib.metadata.entry_points()["dxtbx.scaling_model_ext"]:
+        for entry_point in scaling_model_entry_points:
             if entry_point.name == obj["__id__"]:
                 return entry_point.load().from_dict(obj)
 
diff --git a/src/dxtbx/model/profile.py b/src/dxtbx/model/profile.py
index ba3852586..20ead45f2 100644
--- a/src/dxtbx/model/profile.py
+++ b/src/dxtbx/model/profile.py
@@ -3,6 +3,11 @@
 import importlib.metadata
 import logging
 
+try:
+    profile_entry_points = importlib.metadata.entry_points()["dxtbx.profile_model"]
+except KeyError:
+    profile_entry_points = []
+
 
 class ProfileModelFactory:
     """
@@ -16,7 +21,7 @@ def from_dict(obj):
         """
         if obj is None:
             return None
-        for entry_point in importlib.metadata.entry_points()["dxtbx.profile_model"]:
+        for entry_point in profile_entry_points:
             if entry_point.name == obj["__id__"]:
                 return entry_point.load().from_dict(obj)
         logging.getLogger("dxtbx.model.profile").warn(