diff --git a/simulator-sketch.js b/simulator-sketch.js
index dd8ff70..931a89e 100644
--- a/simulator-sketch.js
+++ b/simulator-sketch.js
@@ -58,7 +58,7 @@ function CPU(mem) {
     add_addr: (addr) => {
       console.log("ADD addr");
       if ( (this.acc + this.memory[addr]) > 15 ) { this.carryFlag = 1; }
-      this.acc = (this.acc + this.memory[addr] % 15);
+      this.acc = ((this.acc + this.memory[addr]) % 15);
       this.instructionPointer = this.instructionPointer += 1;
     },