diff --git a/Firestore/core/src/bundle/bundle_serializer.cc b/Firestore/core/src/bundle/bundle_serializer.cc
index 86942236791..cf120a5a52b 100644
--- a/Firestore/core/src/bundle/bundle_serializer.cc
+++ b/Firestore/core/src/bundle/bundle_serializer.cc
@@ -400,7 +400,8 @@ ResourcePath BundleSerializer::DecodeName(JsonReader& reader,
   }
   auto path =
       ResourcePath::FromString(document_name.get_ref<const std::string&>());
-  if (!rpc_serializer_.IsLocalResourceName(path)) {
+  if (!rpc_serializer_.IsLocalResourceName(path) || path.size() < 5 ||
+      path[4] != "documents") {
     reader.Fail("Resource name is not valid for current instance: " +
                 path.CanonicalString());
     return {};
@@ -647,6 +648,11 @@ BundledDocumentMetadata BundleSerializer::DecodeDocumentMetadata(
   if (!reader.ok()) {
     return {};
   }
+  if (!DocumentKey::IsDocumentKey(path)) {
+    reader.Fail("Resource name is not a valid document key: " +
+                path.CanonicalString());
+    return {};
+  }
   DocumentKey key = DocumentKey(path);
 
   SnapshotVersion read_time = DecodeSnapshotVersion(
@@ -678,6 +684,11 @@ BundleDocument BundleSerializer::DecodeDocument(JsonReader& reader,
   if (!reader.ok()) {
     return {};
   }
+  if (!DocumentKey::IsDocumentKey(path)) {
+    reader.Fail("Resource name is not a valid document key: " +
+                path.CanonicalString());
+    return {};
+  }
   DocumentKey key = DocumentKey(path);
 
   SnapshotVersion update_time = DecodeSnapshotVersion(
diff --git a/Firestore/core/src/remote/serializer.cc b/Firestore/core/src/remote/serializer.cc
index 932064a01a9..ea86a1334c8 100644
--- a/Firestore/core/src/remote/serializer.cc
+++ b/Firestore/core/src/remote/serializer.cc
@@ -1521,7 +1521,8 @@ bool Serializer::IsLocalResourceName(const ResourcePath& path) const {
 
 bool Serializer::IsLocalDocumentKey(absl::string_view path) const {
   auto resource = ResourcePath::FromStringView(path);
-  return IsLocalResourceName(resource) &&
+  return IsLocalResourceName(resource) && resource.size() >= 5 &&
+         resource[4] == "documents" &&
          DocumentKey::IsDocumentKey(resource.PopFirst(5));
 }
 
diff --git a/Firestore/core/test/unit/bundle/bundle_serializer_test.cc b/Firestore/core/test/unit/bundle/bundle_serializer_test.cc
index 72d788c7832..ce59f477266 100644
--- a/Firestore/core/test/unit/bundle/bundle_serializer_test.cc
+++ b/Firestore/core/test/unit/bundle/bundle_serializer_test.cc
@@ -1166,6 +1166,39 @@ TEST_F(BundleSerializerTest, DecodeInvalidBundledDocumentMetadataFails) {
   }
 }
 
+TEST_F(BundleSerializerTest, DecodeNonDocumentKeyResourceNameFails) {
+  // A resource name that points at a collection (odd number of segments after
+  // the `documents` prefix) passes the local-resource-name check but is not a
+  // valid `DocumentKey`. It must be rejected gracefully instead of tripping the
+  // `HARD_ASSERT` inside the `DocumentKey` constructor.
+  {
+    ProtoDocument document = TestDocument(ProtoValue());
+    document.set_name(FullPath("bundle"));
+    std::string json_string;
+    MessageToJsonString(document, &json_string);
+
+    JsonReader reader;
+    bundle_serializer.DecodeDocument(reader, Parse(json_string));
+    EXPECT_NOT_OK(reader.status());
+  }
+
+  {
+    ProtoBundledDocumentMetadata metadata;
+    metadata.set_name(FullPath("bundle"));
+    metadata.set_exists(true);
+    google::protobuf::Timestamp t1;
+    t1.set_seconds(0);
+    t1.set_nanos(0);
+    *metadata.mutable_read_time() = t1;
+    std::string json_string;
+    MessageToJsonString(metadata, &json_string);
+
+    JsonReader reader;
+    bundle_serializer.DecodeDocumentMetadata(reader, Parse(json_string));
+    EXPECT_NOT_OK(reader.status());
+  }
+}
+
 TEST_F(BundleSerializerTest, DecodeTargetWithoutImplicitOrderByOnName) {
   std::string json(
       R"({"name":"myNamedQuery",