diff --git a/lib/opcode.js b/lib/opcode.js
index 3218faf..edf02cb 100644
--- a/lib/opcode.js
+++ b/lib/opcode.js
@@ -67,6 +67,7 @@ Opcode.prototype.toString = function() {
 };
 
 Opcode.smallInt = function(n) {
+  $.checkArgument(_.isNumber(n), 'Invalid Argument: n should be number');
   $.checkArgument(n >= 0 && n <= 16, 'Invalid Argument: n must be between 0 and 16');
   if (n === 0) {
     return Opcode('OP_0');
diff --git a/test/opcode.js b/test/opcode.js
index 6471e13..5de57bd 100644
--- a/test/opcode.js
+++ b/test/opcode.js
@@ -120,10 +120,23 @@ describe('Opcode', function() {
     var testSmallInt = function(n, op) {
       Opcode.smallInt(n).toString().should.equal(op.toString());
     };
+
     for (var i = 0; i < smallints.length; i++) {
       var op = smallints[i];
       it('should work for small int ' + op, testSmallInt.bind(null, i, op));
     }
+
+    it('with not number', function () {
+      Opcode.smallInt.bind(null, '2').should.throw('Invalid Argument');
+    });
+
+    it('with n equal -1', function () {
+      Opcode.smallInt.bind(null, -1).should.throw('Invalid Argument');
+    });
+
+    it('with n equal 17', function () {
+      Opcode.smallInt.bind(null, 17).should.throw('Invalid Argument');
+    });
   });
   describe('@isSmallIntOp', function() {
     var testIsSmallInt = function(op) {