diff --git a/petsctools/options.py b/petsctools/options.py
index ecd715a..0bbe4da 100644
--- a/petsctools/options.py
+++ b/petsctools/options.py
@@ -1126,7 +1126,14 @@ def get(
 
     def getAll(self) -> dict[str, Any]:
         """Return all entries."""
+        # Try to apply type casting to the objects returned by
+        # super().getAll(). Command line arguments with double dashes e.g.
+        # "--opt val" will appear as {"opt": "val"} in
+        # PETSc.Options().getAll(), but PETSc.Options()["opt"] or
+        # PETSc.Options().get("opt") will raise KeyErrors. Passing self.get() a
+        # default value from PETSc.Options().getAll() works around this error
+        # by returning the default when the KeyError is raised.
         return {
-            key: self[key]
+            key: self.get(key, value)
             for key, value in super().getAll().items()
         }
diff --git a/tests/test_options.py b/tests/test_options.py
index ca1d7c2..1d9fcac 100644
--- a/tests/test_options.py
+++ b/tests/test_options.py
@@ -20,6 +20,8 @@ def temporarily_remove_options():
     options = petsctools.Options()
 
     previous_options = dict(options.getAll())
+    # Note that options.clear() does not actually remove all options from
+    # the database - definitely a bug.
     options.clear()
     previous_option_types = petsctools.options._option_types
     petsctools.options._option_types = {}
@@ -28,6 +30,7 @@ def temporarily_remove_options():
 
     yield
 
+    options.clear()
     for k, v in previous_options.items():
         options[k] = v
     petsctools.options._option_types = previous_option_types 
@@ -481,3 +484,48 @@ def test_options_missing_types(setter, deleter):
         for opts in [petsc_opts, petsctools_opts]:
             with pytest.raises(KeyError):
                 opts["my_option"]
+
+
+@pytest.mark.skipnopetsc4py
+def test_getAll_does_type_casting():
+    opts = petsctools.Options()
+    params = {
+        "integer": 666,
+        "float": 12.3,
+        "string": "abc",
+        "bool": False,
+    }
+    for name, value in params.items():
+        opts[name] = value
+
+    # Note that opts.getAll() can contain more than one entry because
+    # PETSc.Options().clear() is bugged, so we get contamination from previous
+    # tests.
+    for name, value in params.items():
+        assert (name, value) in opts.getAll().items()
+
+
+@pytest.mark.skipnopetsc4py
+@pytest.mark.parametrize("backend", ["petsc4py", "petsctools"])
+def test_double_dash_options_do_not_break_getAll(backend):
+    # PETSc.Options.getAll() will include options passed with double-dashes
+    # (e.g. --pdb as 'pdb') but any attempt to access the option with
+    # .get(), __getitem__ etc will raise a KeyError. This test is here to
+    # check that petsctools.Options.getAll() will run without error when '--'
+    # options are passed (even though the result itself is bugged).
+    from petsc4py import PETSc
+
+    opts = petsctools.Options() if backend == "petsctools" else PETSc.Options()
+    opts["--value"] = "xyz"
+
+    # Note that opts.getAll() can contain more than one entry because
+    # PETSc.Options().clear() is bugged, so we get contamination from previous
+    # tests.
+    assert ("value", "xyz") in opts.getAll().items()
+
+    # Check that PETSc have the odd behaviour that we expect - if this fails
+    # then we can undo things!
+    with pytest.raises(KeyError):
+        opts["value"]
+    with pytest.raises(KeyError):
+        opts.getString("value")