diff --git a/src/PyOctoPhaseAssociation.py b/src/PyOctoPhaseAssociation.py
index 2fd2ab0..65e953e 100644
--- a/src/PyOctoPhaseAssociation.py
+++ b/src/PyOctoPhaseAssociation.py
@@ -55,6 +55,11 @@ def main(qml_picks, inventory, velocity_model, lat_min, lat_max, lon_min, lon_ma
                       f"Check if the file(s) is/are correct")
         sys.exit(1)
 
+    if grid_spacing is not None and z_max-z_min < grid_spacing:
+        logging.error(f"The specified grid spacing is larger than the vertical extent of the grid. "
+                      f"Reduce the grid spacing and/or increase the vertical extent of the grid.")
+        sys.exit(1)
+
     #convert input velocity from m/s to km/s
     if p_vel_const is not None:
         p_vel_const = p_vel_const / 1000