diff --git a/spacy_streamlit/visualizer.py b/spacy_streamlit/visualizer.py
index 9567a4e..381f7b1 100644
--- a/spacy_streamlit/visualizer.py
+++ b/spacy_streamlit/visualizer.py
@@ -186,7 +186,7 @@ def visualize_ner(
                 "When the parameter 'manual' is set to True, the parameter 'doc' must be of type 'list', not 'spacy.tokens.Doc'."
             )
     else:
-        labels = labels or [ent.label_ for ent in doc.ents]
+        labels = labels or list({ent.label_ for ent in doc.ents})
 
     if not labels:
         st.warning("The parameter 'labels' should not be empty or None.")