diff --git a/omegaconf/base.py b/omegaconf/base.py
index bd6921a75..85b075209 100644
--- a/omegaconf/base.py
+++ b/omegaconf/base.py
@@ -307,7 +307,11 @@ def _select_impl(
                     throw_on_resolution_failure=throw_on_resolution_failure,
                 )
 
-            assert ret is None or isinstance(ret, Container)
+            if ret is not None and not isinstance(ret, Container):
+                raise ConfigKeyError(
+                    f"Error trying to access {key}: node `{'.'.join(split[0:i + 1])}` "
+                    f"is not a container and thus cannot contain `{split[i + 1]}``"
+                )
             root = ret
 
         if root is None:
diff --git a/tests/test_errors.py b/tests/test_errors.py
index cbb5199fa..551c952fd 100644
--- a/tests/test_errors.py
+++ b/tests/test_errors.py
@@ -1121,3 +1121,16 @@ def test_errors(expected: Expected, monkeypatch: Any) -> None:
                 expected.op(cfg)
             except Exception as e:
                 assert e.__cause__ is None
+
+
+def test_assertion_error(restore_resolvers: Any) -> None:
+    def assert_false() -> None:
+        assert False
+
+    # The purpose of this test is to cover the case where an `AssertionError`
+    # is processed in `format_and_raise()`. Using a resolver to trigger the assertion
+    # error is just one way of achieving this goal.
+    OmegaConf.register_resolver("assert_false", assert_false)
+    c = OmegaConf.create({"trigger": "${assert_false:}"})
+    with pytest.raises(AssertionError):
+        c.trigger
diff --git a/tests/test_interpolation.py b/tests/test_interpolation.py
index 366c56202..0581aedc5 100644
--- a/tests/test_interpolation.py
+++ b/tests/test_interpolation.py
@@ -8,6 +8,7 @@
 
 from omegaconf import Container, IntegerNode, Node, OmegaConf, Resolver, ValidationError
 from omegaconf._utils import _ensure_container
+from omegaconf.errors import ConfigKeyError
 
 
 @pytest.mark.parametrize(  # type:ignore
@@ -106,7 +107,7 @@ def test_merge_with_interpolation() -> None:
 
 def test_non_container_interpolation() -> None:
     cfg = OmegaConf.create(dict(foo=0, bar="${foo.baz}"))
-    with pytest.raises(AssertionError):
+    with pytest.raises(ConfigKeyError):
         cfg.bar