diff --git a/MAVProxy/modules/mavproxy_param.py b/MAVProxy/modules/mavproxy_param.py
index a4da69a43b..3f828b4577 100644
--- a/MAVProxy/modules/mavproxy_param.py
+++ b/MAVProxy/modules/mavproxy_param.py
@@ -387,6 +387,7 @@ def param_bitmask_modify(self, master, args):
         '''command for performing bitmask actions on a parameter'''
 
         BITMASK_ACTIONS = ['toggle', 'set', 'clear']
+        NUM_BITS_MAX = 32
 
         # Ensure we have at least an action and a parameter
         if len(args) < 2:
@@ -474,6 +475,11 @@ def param_bitmask_modify(self, master, args):
             # We don't have enough information to modify the bitmask, so bail
             return
 
+        # Sanity check the bit index
+        if bit_index >= NUM_BITS_MAX:
+            print(f"Cannot perform bitmask action '{action}' on bit index {bit_index}.")
+            return
+
         # We have enough information to try perform an action
         if action == "toggle":
             value = value ^ (1 << bit_index)