diff --git a/src/com/craftinginterpreters/lox/Interpreter.java b/src/com/craftinginterpreters/lox/Interpreter.java
index 57e697c..1d87b87 100644
--- a/src/com/craftinginterpreters/lox/Interpreter.java
+++ b/src/com/craftinginterpreters/lox/Interpreter.java
@@ -119,9 +119,14 @@ class Interpreter implements Expr.Visitor<Object> {
                 }
 
                 throw new RuntimeError(expr.operator, "Operands must be two numbers or two strings.");
-            case SLASH:
+        case SLASH: {
                 checkNumberOperands(expr.operator, left, right);
-                return (double) left / (double) right;
+                double rhs = (double) right;
+                if (rhs == 0) {
+                    throw new RuntimeError(expr.operator, "Division by zero.");
+                }
+                return (double) left / rhs;
+        }
             case STAR:
                 checkNumberOperands(expr.operator, left, right);
                 return (double) left * (double) right;