diff --git a/linkml_runtime/utils/schemaview.py b/linkml_runtime/utils/schemaview.py
index 42b238c9..1867a404 100644
--- a/linkml_runtime/utils/schemaview.py
+++ b/linkml_runtime/utils/schemaview.py
@@ -465,8 +465,7 @@ def imports_closure(
             # visit item
             sn = todo.pop()
             if sn not in self.schema_map:
-                imported_schema = self.load_import(sn)
-                self.schema_map[sn] = imported_schema
+                self.schema_map[sn] = self.load_import(sn)
 
             # resolve item's imports if it has not been visited already
             # we will get duplicates, but not cycles this way, and
@@ -1904,6 +1903,10 @@ def slot_applicable_range_elements(self, slot: SlotDefinition) -> list[ClassDefi
         :param slot:
         :return: list of element types
         """
+        if not slot or not isinstance(slot, SlotDefinition):
+            err_msg = "A SlotDefinition must be provided to generate the slot applicable range elements."
+            raise ValueError(err_msg)
+
         is_any = False
         range_types = []
         for r in self.slot_range_as_union(slot):
@@ -1930,6 +1933,10 @@ def slot_range_as_union(self, slot: SlotDefinition) -> list[ElementName]:
         :param slot:
         :return: list of ranges
         """
+        if not slot or not isinstance(slot, SlotDefinition):
+            err_msg = "A SlotDefinition must be provided to generate the slot range as union."
+            raise ValueError(err_msg)
+
         return list({y.range for y in [slot, *[x for x in [*slot.exactly_one_of, *slot.any_of] if x.range]]})
 
     def induced_slot_range(self, slot: SlotDefinition, strict: bool = False) -> set[str | ElementName]:  # noqa: FBT001, FBT002
@@ -1947,6 +1954,9 @@ def induced_slot_range(self, slot: SlotDefinition, strict: bool = False) -> set[
         :return: set of ranges
         :rtype: set[str | ElementName]
         """
+        if not slot or not isinstance(slot, SlotDefinition):
+            err_msg = "A SlotDefinition must be provided to generate the induced slot range."
+            raise ValueError(err_msg)
 
         slot_range = slot.range
         any_of_range = {x.range for x in slot.any_of if x.range}
diff --git a/tests/test_utils/test_schemaview.py b/tests/test_utils/test_schemaview.py
index c1eef1ed..52511ccd 100644
--- a/tests/test_utils/test_schemaview.py
+++ b/tests/test_utils/test_schemaview.py
@@ -2125,6 +2125,41 @@ def test_slot_range(
         pytest.fail(f"Unexpected range_function value: {range_function}")
 
 
+@pytest.mark.parametrize(
+    "slot_argument",
+    [
+        None,
+        "slot_name",
+        12345,
+        "",
+        set(),
+        {"this": "that"},
+        True,
+        False,
+        lambda x: f"slot {x}",
+        ClassDefinition(name="whatever"),
+        SlotDefinitionName("something"),
+    ],
+)
+@pytest.mark.parametrize(
+    ("range_function", "err_desc"),
+    [
+        ("slot_range_as_union", "slot range as union"),
+        ("induced_slot_range", "induced slot range"),
+        ("slot_applicable_range_elements", "slot applicable range elements"),
+    ],
+)
+def test_range_function_non_slot_input(
+    schema_view_core: SchemaView, slot_argument: Any, range_function: str, err_desc: str
+) -> None:
+    """Ensure that incorrect input to the range function generates an error message.
+
+    The schema content is not important as this is solely for testing errors when calling `range` functions with the wrong argument.
+    """
+    with pytest.raises(ValueError, match=f"A SlotDefinition must be provided to generate the {err_desc}."):
+        getattr(schema_view_core, range_function)(slot_argument)
+
+
 """End of range-related tests. Phew!"""