diff --git a/speclite/filters.py b/speclite/filters.py
index 96eb0dc..1a6251e 100644
--- a/speclite/filters.py
+++ b/speclite/filters.py
@@ -1310,7 +1310,9 @@ def __init__(self, response, wavelength,
             self._response = load_filter(response)
         else:
             self._response = response
-        self._wavelength = validate_wavelength_array(wavelength, min_length=2)
+        # Work with a copy of the wavelength array,
+        # see https://github.com/desihub/speclite/issues/34
+        self._wavelength = validate_wavelength_array(wavelength, min_length=2).copy()
         self.num_wavelength = len(self._wavelength)
 
         # Check if extrapolation would be required.
diff --git a/speclite/tests/test_filters.py b/speclite/tests/test_filters.py
index ec1cbe1..a8b039e 100644
--- a/speclite/tests/test_filters.py
+++ b/speclite/tests/test_filters.py
@@ -223,6 +223,7 @@ def test_response_convolve_with_function():
     with pytest.raises(ValueError):
         filt.convolve_with_function(lambda wlen: 1. * u.m, units=u.erg)
 
+
 def test_response_mag():
     wlen = [1, 2, 3]
     meta = dict(group_name='g', band_name='b')
@@ -239,6 +240,19 @@ def test_response_mag():
                        [1, 3] * default_wavelength_unit)
 
 
+def test_get_ab_maggies_modify_wavelength():
+    """This is a regression test for
+    https://github.com/desihub/speclite/issues/34
+    """
+    filters = load_filters('gaiadr2-BP', 'gaiadr2-RP', 'gaiadr2-G')
+    waves = np.arange(3000, 11000, 0.11)
+    waves0 = waves.copy()
+    flux = waves * 1.
+    filters[0].get_ab_magnitude(flux, waves)
+    assert (waves == waves0).all()
+    # print(np.nonzero(waves != waves0), waves[2249], waves0[2249], waves[40932], waves0[40932])
+
+
 def test_mag_wavelength_units():
     # Check that non-default wavelength units are handled correctly.
     wlen = [1, 2, 3] * u.Angstrom
@@ -254,6 +268,7 @@ def test_mag_wavelength_units():
     m2 = r.get_ab_maggies(flux, wlen)
     assert m1 == m2
 
+
 def test_wavelength_property():
     # Check that the wavelength property is working
     wlen = [1, 2, 3] * u.Angstrom
@@ -262,6 +277,7 @@ def test_wavelength_property():
     assert np.allclose(r.wavelength, r._wavelength)
     assert np.allclose(r.wavelength, validate_wavelength_array(wlen))
 
+
 def test_mag_flux_units():
     # Check that non-default flux units are handled correctly.
     wlen = [1, 2, 3] * u.Angstrom