diff --git a/tests/core/test_export.py b/tests/core/test_export.py
index b999997e..3b8d805f 100644
--- a/tests/core/test_export.py
+++ b/tests/core/test_export.py
@@ -310,3 +310,20 @@ def test_uppercase_content_key_is_stored_lowercase(tmp_path: Path, caplog: pytes
     titles = read_export(export)["titles"]
     assert titles[0]["keys"] == {KID.hex: "aa" * 16}
     assert "different key" not in caplog.text
+
+
+@pytest.mark.parametrize("key", ["zz" * 16, "aa" * 8, "aa" * 32])
+def test_malformed_content_key_skips_the_key_not_the_download(
+    tmp_path: Path, caplog: pytest.LogCaptureFixture, key: str
+) -> None:
+    """A key that is not 16 bytes of hex, as a new DRM system's tool might return, must not stop licensing."""
+    export = tmp_path / "export.json"
+    title = make_title()
+    title.tracks.manifest_url = "https://example.test/m.mpd"
+    runner = make_dl()
+
+    with caplog.at_level(logging.WARNING, logger="download"):
+        runner.write_export(export, title, title.tracks.videos[0], KeyDRM(key))
+
+    assert "keys" not in entry(export)
+    assert f"Not exporting the key for KID {KID.hex}" in caplog.text
diff --git a/unshackle/commands/dl.py b/unshackle/commands/dl.py
index 0abd1d9e..7ca03888 100644
--- a/unshackle/commands/dl.py
+++ b/unshackle/commands/dl.py
@@ -4001,10 +4001,18 @@ class dl:
                         self.log.warning(
                             f"KID {kid.hex} already has a different key in {export}, keeping the existing one"
                         )
-                    else:
+                        continue
+                    try:
                         entry.add_key(kid.hex, key)
+                    except mediaexport.ExportError as e:
+                        # a key the format cannot hold (not 16 bytes of hex) costs the export that key,
+                        # never the download
+                        self.log.warning(f"Not exporting the key for KID {kid.hex}: {e}")
 
-            mediaexport.write(export, doc)
+            try:
+                mediaexport.write(export, doc)
+            except (mediaexport.ExportError, OSError) as e:
+                self.log.warning(f"Could not write export {export}: {e}")
 
     def export_entry(self, title: Title_T) -> mediaexport.Entry:
         """A mediaexport entry for ``title``: manifests, chapters, a small track list, no keys yet."""