diff --git a/vm/vm.cpp b/vm/vm.cpp
index aa7a0f1..4ef3f11 100644
--- a/vm/vm.cpp
+++ b/vm/vm.cpp
@@ -602,23 +602,25 @@ bool VM::execSHRR(void) {
   return true;
 }
 bool VM::execPUSH(void) {
-  // TODO: STACK < 0
   uint8_t src;
 
   src = as.code[regs[IP] + 1];
   DBG_INFO(("PUSH %s\n", getRegName(src)));
+  if (regs[SP] + sizeof(uint16_t) > 0xffff) {
+    DBG_ERROR(("Out of bound: stack is going above 0xFFFF!\n"));
+    return false;
+  }
   memcpy(&as.stack[regs[SP]], &regs[src], sizeof(uint16_t));
   regs[SP] += sizeof(uint16_t);
   return true;
 }
 bool VM::execPOOP(void) {
-  // TODO: STACK < 0
   uint8_t dst;
 
   dst = as.code[regs[IP] + 1];
   DBG_INFO(("POOP %s\n", getRegName(dst)));
   if (regs[SP] - sizeof(uint16_t) < 0) {
-    DBG_ERROR(("Stack is going below 0!\n"));
+    DBG_ERROR(("Out of bound: stack is going below 0!\n"));
     return false;
   }
   regs[SP] -= sizeof(uint16_t);