diff --git a/creature.go b/creature.go
index 85cc0f6..d92c031 100644
--- a/creature.go
+++ b/creature.go
@@ -263,7 +263,7 @@ func (machine *Machine[WORD]) Peek(address WORD) (word WORD) {
 // Poke sets the value at address in the block to word.
 func (machine *Machine[WORD]) Poke(address WORD, word WORD) {
 	if int(address) >= len(machine.block) {
-		reallocatedBlock := make([]WORD, address*3/2)
+		reallocatedBlock := make([]WORD, address*3/2+1)
 		copy(reallocatedBlock, machine.block)
 		machine.block = reallocatedBlock
 	}