Problem with receiving item from npc

I keep getting the same error message no matter what I do, and Ive tried everything I am capable of
Exception: RuntimeError
Message: Script error within event 3 (coords 13,4), map 79 (Serenity Beach):
Exception: NameError
Message: (eval):1:in `pbExecuteScript'undefined local variable or method `kernel' for #<Interpreter:0xed2f298>
***Full script:
kernel.pbReceiveItem(:POTION)

Interpreter:243:in `pbExecuteScript'
Interpreter:1606:in `eval'
Interpreter:243:in `pbExecuteScript'
Interpreter:1606:in `command_355'
Interpreter:494:in `execute_command'
Interpreter:193:in `update'
Interpreter:106:in `loop'
Interpreter:198:in `update'
Scene_Map:163:in `update'
Scene_Map:161:in `loop'

Interpreter:276:in `pbExecuteScript'
Interpreter:1606:in `command_355'
Interpreter:494:in `execute_command'
Interpreter:193:in `update'
Interpreter:106:in `loop'
Interpreter:198:in `update'
Scene_Map:163:in `update'
Scene_Map:161:in `loop'
Scene_Map:170:in `update'
Scene_Map:234:in `main'

I would appreciate some help since this is very frustrating and discouraging

Try using an uppercase K, like Kernel.pbReceiveItem(:POTION)

It worked, thank you so much! I can't believe I spent hours trying to fix it and I didn't even notice. I'll have to be more careful next time!