diff --git a/autotest/t023_test.py b/autotest/t023_test.py
index 5faf0a072f..6d065a270e 100644
--- a/autotest/t023_test.py
+++ b/autotest/t023_test.py
@@ -30,6 +30,8 @@ def test_mt3d_multispecies():
     sconc3 = np.random.random((nrow, ncol))
     btn = flopy.mt3d.Mt3dBtn(mt, ncomp=ncomp, sconc=1., sconc2=2.,
                              sconc3=sconc3, sconc5=5.)
+    # check obs I/O
+    mt.btn.obs = np.array([[0, 2, 300], [0, 1, 250]])
     crch32 = np.random.random((nrow, ncol))
     cevt33 = np.random.random((nrow, ncol))
     ssm = flopy.mt3d.Mt3dSsm(mt, crch=1., crch2=2., crch3={2:crch32}, crch5=5.,
@@ -49,6 +51,8 @@ def test_mt3d_multispecies():
     # Load the MT3D model into mt2 and then write it out
     fname = modelname + '.nam'
     mt2 = flopy.mt3d.Mt3dms.load(fname, model_ws=testpth, verbose=True)
+    # check obs I/O
+    assert np.all(mt.btn.obs == mt2.btn.obs)
     mt2.name = modelname2
     mt2.write_input()
 
diff --git a/flopy/mt3d/mtbtn.py b/flopy/mt3d/mtbtn.py
index 1a68d89458..5458669d3b 100644
--- a/flopy/mt3d/mtbtn.py
+++ b/flopy/mt3d/mtbtn.py
@@ -882,7 +882,7 @@ def load(f, model, ext_unit_dict=None):
                 i = int(line[10:20])
                 j = int(line[20:30])
                 obs.append([k, i, j])
-            obs = np.array(obs)
+            obs = np.array(obs) - 1
             if model.verbose:
                 print('   OBS {}'.format(obs))