diff --git a/lib/bn.js b/lib/bn.js
index 8532b5b..703e9ef 100644
--- a/lib/bn.js
+++ b/lib/bn.js
@@ -1056,6 +1056,7 @@
     var bl9 = b9 & 0x1fff;
     var bh9 = b9 >>> 13;
 
+    out.negative = self.negative ^ num.negative;
     out.length = 19;
     /* k = 0 */
     lo = Math.imul(al0, bl0);
diff --git a/test/arithmetic-test.js b/test/arithmetic-test.js
index c87fe31..e51a7f1 100644
--- a/test/arithmetic-test.js
+++ b/test/arithmetic-test.js
@@ -159,12 +159,21 @@ describe('BN.js/Arithmetic', function () {
   function testMethod (name, mul) {
     describe(name, function () {
       it('should multiply numbers of different signs', function () {
-        assert.equal(mul(new BN(0x1001), new BN(0x1234)).toString(16),
-          '1235234');
-        assert.equal(mul(new BN(-0x1001), new BN(0x1234)).toString(16),
-          '-1235234');
-        assert.equal(mul(new BN(-0x1001), new BN(-0x1234)).toString(16),
-          '1235234');
+        var offsets = [
+          1, // smallMulTo
+          250, // comb10MulTo
+          1000, // bigMulTo
+          15000 // jumboMulTo
+        ];
+
+        for (var i = 0; i < offsets.length; ++i) {
+          var x = new BN(1).ishln(offsets[i]);
+
+          assert.equal(mul(x, x).isNeg(), false);
+          assert.equal(mul(x, x.neg()).isNeg(), true);
+          assert.equal(mul(x.neg(), x).isNeg(), true);
+          assert.equal(mul(x.neg(), x.neg()).isNeg(), false);
+        }
       });
 
       it('should multiply with carry', function () {
diff --git a/util/genCombMulTo.js b/util/genCombMulTo.js
index 242354a..8b456c7 100644
--- a/util/genCombMulTo.js
+++ b/util/genCombMulTo.js
@@ -23,6 +23,7 @@ function genCombMulTo (alen, blen) {
     src.push('var bh' + i + ' = b' + i + ' >>> 13;');
   }
   src.push('');
+  src.push('out.negative = self.negative ^ num.negative;');
   src.push('out.length = ' + len + ';');
 
   for (var k = 0; k < len; k++) {
diff --git a/util/genCombMulTo10.js b/util/genCombMulTo10.js
index c87c19d..4214ffd 100644
--- a/util/genCombMulTo10.js
+++ b/util/genCombMulTo10.js
@@ -22,6 +22,7 @@ function genCombMulTo (alen, blen) {
     src.push('var bh' + i + ' = b' + i + ' >>> 13;');
   }
   src.push('');
+  src.push('out.negative = self.negative ^ num.negative;');
   src.push('out.length = ' + len + ';');
 
   for (var k = 0; k < len; k++) {