diff --git a/lang/vm.c b/lang/vm.c
index abb4152..f9a38ec 100644
--- a/lang/vm.c
+++ b/lang/vm.c
@@ -2,6 +2,7 @@
 // Copyright (c) 2023 John Watts and the LuminaSensum contributors
 
 #include "vm.h"
+#include "error.h"
 #include "object.h"
 #include <stddef.h>
 #include <stdlib.h>
@@ -10,14 +11,16 @@
 	Object *stack;
 	int stack_base;
 	int stack_next;
+	int stack_size;
 };
 
 VmState vm_create(void) {
 	struct vm_state *state = malloc(sizeof(struct vm_state));
-	Object *stack = malloc(sizeof(Object) * 16);
-	state->stack = stack;
+	state->stack_size = 16;
 	state->stack_base = 0;
 	state->stack_next = 0;
+	Object *stack = malloc(sizeof(Object) * state->stack_size);
+	state->stack = stack;
 	return (VmState)state;
 }
 
@@ -30,7 +33,10 @@
 
 void vm_stack_set(VmState state, int index, Object obj) {
 	struct vm_state *priv = (struct vm_state *)state;
-	Object *stack_pos = &priv->stack[priv->stack_base + index];
+	int offset = priv->stack_base + index;
+	abort_if(index < 0, "vm_stack_set: negative value");
+	abort_if(offset >= priv->stack_next, "vm_stack_set: stack overflow");
+	Object *stack_pos = &priv->stack[offset];
 	Object old = *stack_pos;
 	if (old != NULL) {
 		object_drop(stack_pos);
@@ -40,7 +46,10 @@
 
 Object vm_stack_get(VmState state, int index) {
 	struct vm_state *priv = (struct vm_state *)state;
-	Object obj = priv->stack[priv->stack_base + index];
+	int offset = priv->stack_base + index;
+	abort_if(index < 0, "vm_stack_get: negative value");
+	abort_if(offset >= priv->stack_next, "vm_stack_get: stack overflow");
+	Object obj = priv->stack[offset];
 	if (obj != NULL) {
 		object_hold(obj);
 	}
@@ -49,11 +58,19 @@
 
 void vm_stack_push(VmState state, Object obj) {
 	struct vm_state *priv = (struct vm_state *)state;
+	// stack_next starts at 0, stack_size starts at 1
+	// Convert stack_size to a max stack offset to compensate
+	int max_stack = priv->stack_size - 1;
+	// Check if stack_next is outside the stack before
+	// writing to it
+	abort_if(priv->stack_next > max_stack, "vm_stack_push: stack overflow");
 	priv->stack[priv->stack_next++] = obj;
 }
 
 Object vm_stack_pop(VmState state) {
 	struct vm_state *priv = (struct vm_state *)state;
+	abort_if(priv->stack_next <= priv->stack_base,
+		"vm_stack_pop: stack base underflow");
 	Object obj = priv->stack[--priv->stack_next];
 	priv->stack[priv->stack_next] = NULL;
 	return obj;