diff --git a/src/gstools/normalizer/methods.py b/src/gstools/normalizer/methods.py
index ded75eb7..bcedb8e3 100644
--- a/src/gstools/normalizer/methods.py
+++ b/src/gstools/normalizer/methods.py
@@ -345,7 +345,7 @@ def denormalize_range(self):
         if np.isclose(self.lmbda, 0):
             return (-np.inf, np.inf)
         if self.lmbda < 0:
-            return (-np.inf, np.divide(1, self.lmbda))
+            return (-np.inf, -np.divide(1, self.lmbda))
         return (-np.divide(1, self.lmbda), np.inf)
 
     def _denormalize(self, data):
diff --git a/tests/test_normalizer.py b/tests/test_normalizer.py
index 9ab0f45e..62173e4f 100644
--- a/tests/test_normalizer.py
+++ b/tests/test_normalizer.py
@@ -145,6 +145,26 @@ def test_manly(self):
             )
         )
 
+    def test_manly_negative_lambda(self):
+        values = np.array([-2.0, -1.0, 0.0, 1.0, 2.0, np.nan])
+        for lmbda in (-1.0, -0.5, -0.1):
+            with self.subTest(lmbda=lmbda):
+                normalizer = gs.normalizer.Manly(lmbda=lmbda)
+                np.testing.assert_allclose(
+                    normalizer.denormalize(normalizer.normalize(values)),
+                    values,
+                )
+
+    def test_manly_inverse_domain(self):
+        normalizer = gs.normalizer.Manly(lmbda=-1.0)
+        np.testing.assert_allclose(
+            normalizer.denormalize([-1.0, 0.0, 0.5]),
+            [-np.log(2.0), 0.0, np.log(2.0)],
+        )
+        with self.assertWarns(UserWarning):
+            result = normalizer.denormalize([1.0, 2.0])
+        self.assertTrue(np.all(np.isnan(result)))
+
     def test_parameterless(self):
         no = gs.normalizer.LogNormal()
         self.assertTrue(