diff --git a/pyleoclim/tests/test_core_Series.py b/pyleoclim/tests/test_core_Series.py
index 8fcea6f1..4dd30b88 100644
--- a/pyleoclim/tests/test_core_Series.py
+++ b/pyleoclim/tests/test_core_Series.py
@@ -1084,7 +1084,7 @@ def test_xwave_t6(self):
        tau = ts1.time[::10]
        _ = ts1.wavelet_coherence(ts2,method='wwz',settings={'tau':tau})
        
-    @pytest.mark.parametrize('freq', [None,np.linspace(1/100,1/2,num=20),'log', 'nfft', 'welch'])
+    @pytest.mark.parametrize('freq', [None,np.linspace(1/100,1/2,num=20),'log', 'nfft', 'welch','scale'])
     def test_xwave_t7(self, freq):
        ''' Test Series.wavelet_coherence() with freq method argument
        '''
diff --git a/pyleoclim/utils/wavelet.py b/pyleoclim/utils/wavelet.py
index 5e0ad6d9..60c08613 100644
--- a/pyleoclim/utils/wavelet.py
+++ b/pyleoclim/utils/wavelet.py
@@ -1928,7 +1928,7 @@ def freq_vector_scale(ts, dj=0.25, s0=None,j1=None, mother='MORLET',param=None):
 
     j = np.arange(0, j1 + 1)
     scale = s0 * 2. ** (j * dj)
-    freq = 1. / (fourier_factor * scale)       
+    freq = np.sort(1. / (fourier_factor * scale)) # ensure increasing order     
 
     return freq