diff --git a/bsmetadata/hydra_configs/v2.yaml b/bsmetadata/hydra_configs/v2.yaml
index ee6a6a5d..8ace0fe9 100644
--- a/bsmetadata/hydra_configs/v2.yaml
+++ b/bsmetadata/hydra_configs/v2.yaml
@@ -48,6 +48,7 @@ data_config:
     metadata_prefix_sep: ' |||'
     metadata_prefix_start_seq: ''
     max_seq_len: 1024
+    apply_cm3_loss_to_sequences: false
     html_parser_config:
       all_tags_rules:
         attributes_to_keep:
diff --git a/bsmetadata/metadata_processors.py b/bsmetadata/metadata_processors.py
index 755041f6..b153051b 100644
--- a/bsmetadata/metadata_processors.py
+++ b/bsmetadata/metadata_processors.py
@@ -174,6 +174,10 @@ class MetadataConfig:
     max_seq_len: int = field(
         default=512, metadata={"help": "The maximum number of tokens to use for each training chunk."}
     )
+    apply_cm3_loss_to_sequences: bool = field(
+        default=False,
+        metadata={"help": "If True, the CM3 loss will be applied to training input sequences. "},
+    )
     html_parser_config: Optional[HTMLParserConfig] = HTMLParserConfig(
         AllTagsRules(
             attributes_to_keep=None,
diff --git a/bsmetadata/metadata_utils.py b/bsmetadata/metadata_utils.py
index baa632c2..87371b5b 100644
--- a/bsmetadata/metadata_utils.py
+++ b/bsmetadata/metadata_utils.py
@@ -120,10 +120,31 @@ def is_metadata(idx: int) -> bool:
         # Create chunks of `max_seq_len` tokens.
         prefix_len = len(metadata_prefix_encoded)
         max_text_len = cfg.max_seq_len - prefix_len
+        if cfg.apply_cm3_loss_to_sequences:
+            max_text_len -= 2
 
         for text_chunk_encoded, chunk_metadata_mask in chunks(
             max_text_len, text_with_local_metadata_encoded.input_ids, token_level_metadata_mask
         ):
+            if cfg.apply_cm3_loss_to_sequences:
+                span_ids = sorted([random.randint(0, len(text_chunk_encoded)) for x in range(2)])
+                span_start, span_end = span_ids[0], span_ids[1]
+                if span_end - span_start > 0:
+                    text_chunk_encoded = (
+                        text_chunk_encoded[:span_start]
+                        + [tokenizer.mask_token_id]
+                        + text_chunk_encoded[span_end:]
+                        + [tokenizer.mask_token_id]
+                        + text_chunk_encoded[span_start:span_end]
+                    )
+                    chunk_metadata_mask = (
+                        chunk_metadata_mask[:span_start]
+                        + [1]
+                        + chunk_metadata_mask[span_end:]
+                        + [1]
+                        + chunk_metadata_mask[span_start:span_end]
+                    )
+
             total_len = prefix_len + len(text_chunk_encoded)
             padding_len = max_text_len - len(text_chunk_encoded)
 
diff --git a/bsmetadata/train.py b/bsmetadata/train.py
index b0b46428..825e6eda 100644
--- a/bsmetadata/train.py
+++ b/bsmetadata/train.py
@@ -278,10 +278,16 @@ def main(args: CFG) -> None:
         new_tokens = [
             AddedToken(token, rstrip=False, lstrip=False, single_word=False, normalized=False) for token in new_tokens
         ]
-        tokenizer = AutoTokenizer.from_pretrained(args.model_name, additional_special_tokens=new_tokens)
     else:
-        tokenizer = AutoTokenizer.from_pretrained(args.model_name)
+        new_tokens = []
+
+    new_tokens += [AddedToken("<MASK>", rstrip=False, lstrip=False, single_word=False, normalized=False)]
+    tokenizer = AutoTokenizer.from_pretrained(args.model_name, additional_special_tokens=new_tokens)
+
+    tokenizer.mask_token = "<MASK>"
+    tokenizer.mask_token_id = tokenizer.convert_tokens_to_ids(tokenizer.mask_token)
     tokenizer.pad_token = tokenizer.eos_token
+
     if args.data_config.experiment == "with_metadata_datasetv2_tf":
         from bsmetadata.experiments.with_metadata_datasetv2_tf import get_dataloader, get_dummy_dataloader