diff --git a/src/Model/Geometry/ProfileXYZ.py b/src/Model/Geometry/ProfileXYZ.py
index 41381a04..323fb9bc 100644
--- a/src/Model/Geometry/ProfileXYZ.py
+++ b/src/Model/Geometry/ProfileXYZ.py
@@ -881,25 +881,31 @@ class ProfileXYZ(Profile, SQLSubModel):
 
         # Interpolate points at river left side
         if (i_left > 0):
-            fact = (z - self.point(i_left).z) / (self.point(i_left - 1).z
-                                                 - self.point(i_left).z)
-            x = self.point(i_left).x + fact * (self.point(i_left - 1).x
-                                               - self.point(i_left).x)
-            y = self.point(i_left).y + fact * (self.point(i_left - 1).y
-                                               - self.point(i_left).y)
-            pt_left = PointXYZ(x=x, y=y, z=z, name="wl_left")
+            if abs(self.point(i_left - 1).z - self.point(i_left).z) < 1e-20:
+                pt_left = self.point(i_left)
+            else:
+                fact = (z - self.point(i_left).z) / (self.point(i_left - 1).z
+                                                    - self.point(i_left).z)
+                x = self.point(i_left).x + fact * (self.point(i_left - 1).x
+                                                - self.point(i_left).x)
+                y = self.point(i_left).y + fact * (self.point(i_left - 1).y
+                                                - self.point(i_left).y)
+                pt_left = PointXYZ(x=x, y=y, z=z, name="wl_left")
         else:
             pt_left = self.point(0)
 
         # Interpolate points at river right side
         if (i_right < self.number_points - 1):
-            fact = (z - self.point(i_right).z) / (self.point(i_right + 1).z -
-                                                  self.point(i_right).z)
-            x = self.point(i_right).x + fact * (self.point(i_right + 1).x -
-                                                self.point(i_right).x)
-            y = self.point(i_right).y + fact * (self.point(i_right + 1).y -
-                                                self.point(i_right).y)
-            pt_right = PointXYZ(x=x, y=y, z=z, name="wl_right")
+            if abs(self.point(i_right + 1).z - self.point(i_right).z) < 1e-20:
+                pt_right = self.point(i_right)
+            else:
+                fact = (z - self.point(i_right).z) / \
+                        (self.point(i_right + 1).z - self.point(i_right).z)
+                x = self.point(i_right).x + fact * \
+                        (self.point(i_right + 1).x - self.point(i_right).x)
+                y = self.point(i_right).y + fact * \
+                        (self.point(i_right + 1).y - self.point(i_right).y)
+                pt_right = PointXYZ(x=x, y=y, z=z, name="wl_right")
         else:
             pt_right = self.point(self.number_points - 1)