diff --git a/src/py_eddy_tracker/observations/network.py b/src/py_eddy_tracker/observations/network.py
index 0e5b9576..4f9af0b3 100644
--- a/src/py_eddy_tracker/observations/network.py
+++ b/src/py_eddy_tracker/observations/network.py
@@ -1464,7 +1464,7 @@ def date2file(julian_day):
                         _t,
                         i_target_f,
                         pct_target_f,
-                        delta_t=dt_advect,
+                        n_days=dt_advect,
                     )
 
                 itf_final[slice_track] = i_target_f
@@ -1495,7 +1495,7 @@ def date2file(julian_day):
                         _t,
                         i_target_b,
                         pct_target_b,
-                        delta_t=-dt_advect,
+                        n_days=-dt_advect,
                     )
 
                 itb_final[slice_track] = i_target_b
diff --git a/src/py_eddy_tracker/observations/observation.py b/src/py_eddy_tracker/observations/observation.py
index 0dc4ed69..557c0279 100644
--- a/src/py_eddy_tracker/observations/observation.py
+++ b/src/py_eddy_tracker/observations/observation.py
@@ -2056,7 +2056,8 @@ def contains(self, x, y, intern=False):
         xname, yname = self.intern(intern)
         m = ~(isnan(x) + isnan(y))
         i = -ones(x.shape, dtype="i4")
-        if x.size != 0:
+
+        if x.size != 0 and m.any():
             i[m] = poly_indexs(x[m], y[m], self[xname], self[yname])
         return i
 
diff --git a/src/py_eddy_tracker/poly.py b/src/py_eddy_tracker/poly.py
index fc36185b..0f0271ee 100644
--- a/src/py_eddy_tracker/poly.py
+++ b/src/py_eddy_tracker/poly.py
@@ -854,8 +854,8 @@ def poly_indexs(x_p, y_p, x_c, y_c):
     """
     Index of contour for each postion inside a contour, -1 in case of no contour
 
-    :param array x_p: longitude to test (must be define, no nan)
-    :param array y_p: latitude to test (must be define, no nan)
+    :param array x_p: longitude to test (must be defined, no nan)
+    :param array y_p: latitude to test (must be defined, no nan)
     :param array x_c: longitude of contours
     :param array y_c: latitude of contours
     """