diff --git a/modules/evaluate.py b/modules/evaluate.py
index 61e30261..866d7f90 100644
--- a/modules/evaluate.py
+++ b/modules/evaluate.py
@@ -82,7 +82,12 @@ def calculate_perplexity(models, input_dataset, stride, _max_length):
         yield cumulative_log + "Tokenizing the input dataset...\n\n"
         encodings = encode(text, add_special_tokens=False)
         seq_len = encodings.shape[1]
-        max_length = _max_length or shared.model.config.max_position_embeddings
+        if not _max_length:
+            if hasattr(shared.model.config, 'max_position_embeddings'):
+                max_length = shared.model.config.max_position_embeddings
+            else:
+                max_length = 2048
+
         nlls = []
         prev_end_loc = 0
         for begin_loc in tqdm(range(0, seq_len, stride)):