diff --git a/num.js b/num.js
index 9a09ada..d2ccda5 100644
--- a/num.js
+++ b/num.js
@@ -12,6 +12,12 @@ function Num(num, prec) {
         return self;
     }
 
+    if (num instanceof int) {
+        this._int = num;
+        this._precision = prec || 0;
+        return self;
+    }
+
     // convert to a string
     num = '' + num;
 
@@ -28,7 +34,11 @@ function Num(num, prec) {
     }
 
     this._int = int(num);
-    this._precision = prec || precision;
+    this._precision = precision;
+
+    if (prec && prec > 0) {
+        this.set_precision(prec);
+    }
 }
 
 // TODO (shtylman) cleanup
diff --git a/test/build.js b/test/build.js
index fa0c6b7..8bfb471 100644
--- a/test/build.js
+++ b/test/build.js
@@ -36,8 +36,8 @@ test('build', function() {
 });
 
 test('build#precision', function() {
-    assert.equal(num(15, 1), '1.5');
-    assert.equal(num(1234567890, 5), '12345.67890');
-    assert.equal(num(-122, 4), '-0.0122');
+    assert.equal(num(15, 1), '15.0');
+    assert.equal(num(1234567890, 5).div(10e4), '12345.67890');
+    assert.equal(num(-122, 4).div(10e3), '-0.0122');
 });