diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index 3b5897f..dccb39e 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -6,6 +6,7 @@ version 1.0.7 (unreleased)
 --------------------------
 - Fix algorithm convergence for the `kappa` distribution.
 - Added Python 3.12 to the test suite and supported versions.
+- Avoid inplace modifications of input arrays in ``lmom_ratios``.
 
 version 1.0.6 (2023-07-06)
 --------------------------
diff --git a/lmoments3/__init__.py b/lmoments3/__init__.py
index 67aab44..7cc3004 100644
--- a/lmoments3/__init__.py
+++ b/lmoments3/__init__.py
@@ -86,7 +86,7 @@ def _samlmularge(x, nmom=5):
     try:
         x = np.asarray(x, dtype=np.float64)
         n = len(x)
-        x.sort()
+        x = np.sort(x)
     except ValueError:
         raise ValueError("Input data to estimate L-moments must be numeric.")
 
@@ -142,7 +142,7 @@ def _samlmusmall(x, nmom=5):
     try:
         x = np.asarray(x, dtype=np.float64)
         n = len(x)
-        x.sort()
+        x = np.sort(x)
     except ValueError:
         raise ValueError("Input data to estimate L-moments must be numeric.")
 
diff --git a/lmoments3/distr.py b/lmoments3/distr.py
index 3c17b34..c87c5ab 100644
--- a/lmoments3/distr.py
+++ b/lmoments3/distr.py
@@ -48,7 +48,7 @@ def _lmom_ratios(self, *shapes, locs, scale, nmom):
         """When overriding, *shapes can be replaced by the actual distribution's shape parameter(s), if any."""
         raise NotImplementedError
 
-    def lmom_fit(self, data=[], lmom_ratios=[]):
+    def lmom_fit(self, data=None, lmom_ratios=None):
         """Fit the distribution function to the given data or given L-moments.
 
         :param data: Data to use in calculating the distribution parameters
@@ -59,11 +59,11 @@ def lmom_fit(self, data=[], lmom_ratios=[]):
         :rtype: :class:`OrderedDict`
         """
         n_min = self.numargs + 2
-        if len(data) > 0:
+        if data is not None:
             if len(data) <= n_min:
                 raise ValueError(f"At least {n_min} data points must be provided.")
             lmom_ratios = lm.lmom_ratios(data, nmom=n_min)
-        elif not lmom_ratios:
+        elif lmom_ratios is None:
             raise Exception("Either `data` or `lmom_ratios` must be provided.")
         elif len(lmom_ratios) < n_min:
             raise ValueError(f"At least {n_min} number of L-moments must be provided.")
diff --git a/lmoments3/tests/test_lmoments.py b/lmoments3/tests/test_lmoments.py
index 8813cf5..d224609 100644
--- a/lmoments3/tests/test_lmoments.py
+++ b/lmoments3/tests/test_lmoments.py
@@ -1,5 +1,6 @@
 import unittest
 
+import numpy as np
 from numpy.testing import assert_almost_equal
 
 import lmoments3 as lm
@@ -9,10 +10,12 @@
 
 class TestLmoments(unittest.TestCase):
     def test_samlmu(self):
-        testdata = [2.0, 3.0, 4.0, 2.4, 5.5, 1.2, 5.4, 2.2, 7.1, 1.3, 1.5]
+        testdata = np.array([2.0, 3.0, 4.0, 2.4, 5.5, 1.2, 5.4, 2.2, 7.1, 1.3, 1.5])
         expected = [3.23636364, 1.14181818, 0.27388535, 0.02335456, -0.04246285]
         result = lm.lmom_ratios(testdata)
         assert_almost_equal(result, expected)
+        # Ensure input was not modified by `lmom_ratios`.
+        assert all(testdata[-3:] == [7.1, 1.3, 1.5])
 
     def test_aic(self):
         data = [