diff --git a/src/nooa/storage/snapshot_vars.py b/src/nooa/storage/snapshot_vars.py
index 6973e0014..f8f1fba6e 100644
--- a/src/nooa/storage/snapshot_vars.py
+++ b/src/nooa/storage/snapshot_vars.py
@@ -55,6 +55,15 @@ def __getitem__(self, key: str) -> Any:
         return self._data[key]
 
     def __setitem__(self, key: str, value: Any) -> None:
+        if not isinstance(key, str):
+            logger.warning(
+                "SnapshotVars: key %r (%s) is not a string and will NOT be persisted "
+                "(it won't survive /exit + resume): snapshots are JSON, which requires "
+                "string keys",
+                key,
+                type(key).__name__,
+            )
+            return
         try:
             serialize(value)
         except (SerializationError, TypeError, ValueError, RecursionError) as exc:
diff --git a/tests/storage/test_snapshot_vars.py b/tests/storage/test_snapshot_vars.py
index 0b7f0ce8b..c0b04b4ca 100644
--- a/tests/storage/test_snapshot_vars.py
+++ b/tests/storage/test_snapshot_vars.py
@@ -71,6 +71,13 @@ def test_snapshot_serialize_succeeds_even_after_bad_write(self):
         assert blob["__type__"] == "dict_class"
         assert blob["data"]["_data"] == {"keep": {"token": "abc"}}
 
+    def test_snapshot_serialize_succeeds_even_after_non_string_key_write(self):
+        v = SnapshotVars()
+        v["keep"] = {"token": "abc"}
+        v[123] = "bad key"  # skipped on write
+        blob, _allow = serialize(v)
+        assert blob["data"]["_data"] == {"keep": {"token": "abc"}}
+
     def test_round_trip_preserves_kept_values(self):
         from nooa.storage.serialization import deserialize