diff --git a/lexicons/vader_lexicon_ptbr.txt b/lexicons/vader_lexicon_ptbr.txt
index 12d0c63..d63a10a 100644
--- a/lexicons/vader_lexicon_ptbr.txt
+++ b/lexicons/vader_lexicon_ptbr.txt
@@ -4670,6 +4670,10 @@ pessimista	-1.5	1.36015	[-1, -3, 1, -2, -2, -2, 1, -3, -2, -2]
 pessimista	-1.5	1.43178	[-3, -1, -1, 1, -3, -3, -2, -2, -2, 1]
 pessimista	-2.0	1.0	[-1, -1, -3, -4, -2, -1, -1, -3, -2, -2]
 pessimistas	-1.0	1.26491	[-1, 1, -1, 0, -2, -2, -2, -3, -1, 1]
+pessima	-3.1	1.04403	[-4, -4, -3, -1, -3, -4, -2, -2, -4, -4]
+pessimas	-3.1	1.04403	[-4, -4, -3, -1, -3, -4, -2, -2, -4, -4]
+pessimo	-3.1	1.04403	[-4, -4, -3, -1, -3, -4, -2, -2, -4, -4]
+pessimos	-3.1	1.04403	[-4, -4, -3, -1, -3, -4, -2, -2, -4, -4]
 petrificacao	-1.9	1.3	[-3, -2, -1, -4, -3, 0, -1, 0, -2, -3]
 petrificacoes	-0.3	1.00499	[0, -1, 0, 0, 0, 0, 0, 0, -3, 1]
 petrificacao	-0.1	1.44568	[-1, 2, -1, -1, 0, 2, 2, -2, -1, -1]
diff --git a/tests/test_sentiment.py b/tests/test_sentiment.py
new file mode 100644
index 0000000..6959dc3
--- /dev/null
+++ b/tests/test_sentiment.py
@@ -0,0 +1,17 @@
+from unittest import TestCase
+
+from leia import SentimentIntensityAnalyzer
+
+
+class PortugueseLexiconTests(TestCase):
+    def setUp(self):
+        self.analyzer = SentimentIntensityAnalyzer()
+
+    def test_pessimo_is_classified_as_negative(self):
+        for word in ("péssimo", "péssima", "péssimos", "péssimas"):
+            with self.subTest(word=word):
+                scores = self.analyzer.polarity_scores(
+                    f"O atendimento foi {word}"
+                )
+                self.assertLess(scores["compound"], -0.05)
+                self.assertGreater(scores["neg"], 0)