diff --git a/lime/lime_text.py b/lime/lime_text.py
index b9716b7f..6223a797 100644
--- a/lime/lime_text.py
+++ b/lime/lime_text.py
@@ -468,11 +468,11 @@ def distance_fn(x):
             return sklearn.metrics.pairwise.pairwise_distances(
                 x, x[0], metric=distance_metric).ravel() * 100
 
-        doc_size = indexed_string.num_words()
-        sample = self.random_state.randint(1, doc_size + 1, num_samples - 1)
-        data = np.ones((num_samples, doc_size))
-        data[0] = np.ones(doc_size)
-        features_range = range(doc_size)
+        vocab_size = indexed_string.num_words()
+        sample = self.random_state.randint(1, vocab_size + 1, num_samples - 1)
+        data = np.ones((num_samples, vocab_size))
+        data[0] = np.ones(vocab_size)
+        features_range = range(vocab_size)
         inverse_data = [indexed_string.raw_string()]
         for i, size in enumerate(sample, start=1):
             inactive = self.random_state.choice(features_range, size,