@@ -2722,9 +2722,15 @@ mod _sqlite3 {
             vm: &VirtualMachine,
         ) -> PyResult<c_int> {
             let mut index = index.try_to_primitive::<isize>(vm).map_err(|_| {
+                let class = object.class();
+                let type_name = class.slot_name();
+                let mut end = type_name.len().min(200);
+                while !type_name.is_char_boundary(end) {
+                    end -= 1;
+                }
                 vm.new_index_error(format!(
                     "cannot fit '{}' into an index-sized integer",
-                    object.class().name()
+                    &type_name[..end]
                 ))
             })?;
             if index < 0 {
 
@@ -113,6 +113,14 @@ def __index__(self):
             with test.assertRaisesRegex(IndexError, message):
                 blob[index] = 0
 
+    for name, bounded_name in (("X" * 250, "X" * 200), ("€" * 67, "€" * 66)):
+        long_index = type(name, (), {"__index__": lambda self: sys.maxsize + 1})()
+        message = f"^cannot fit '{bounded_name}' into an index-sized integer$"
+        with test.assertRaisesRegex(IndexError, message):
+            blob[long_index]
+        with test.assertRaisesRegex(IndexError, message):
+            blob[long_index] = 0
+
     with test.assertRaisesRegex(OverflowError, "^index conversion failed$"):
         blob[BrokenBlobIndex()]
     with test.assertRaisesRegex(OverflowError, "^index conversion failed$"):