diff --git a/lib/function/algebra/simplify/simplifyCore.js b/lib/function/algebra/simplify/simplifyCore.js
index b290fafc1..987807da5 100644
--- a/lib/function/algebra/simplify/simplifyCore.js
+++ b/lib/function/algebra/simplify/simplifyCore.js
@@ -49,6 +49,9 @@ function factory(type, config, load, typed, math) {
           if (type.isConstantNode(a1) && a1.value === "0") {
               return a0;
           }
+          if (node.args.length === 2 && type.isOperatorNode(a1) && a1.op === '-' && a1.fn === 'unaryMinus') {
+              return new OperatorNode('-', 'subtract', [a0,a1.args[0]]);
+          }
           return new OperatorNode(node.op, node.fn, a1 ? [a0,a1] : [a0]);
       } else if (node.op === "-") {
           if (type.isConstantNode(a0) && a1) {
@@ -58,7 +61,7 @@ function factory(type, config, load, typed, math) {
                   return new OperatorNode("-", "unaryMinus", [a1]);
               }
           }
-          if (node.fn === "subtract") {
+          if (node.fn === "subtract" && node.args.length === 2) {
               if (type.isConstantNode(a1) && a1.value === "0") {
                   return a0;
               }
@@ -67,8 +70,14 @@ function factory(type, config, load, typed, math) {
               }
               return new OperatorNode(node.op, node.fn, [a0,a1]);
           } else if (node.fn === "unaryMinus") {
+              if (type.isOperatorNode(a0)) {
+                  if (a0.fn === 'unaryMinus') {
+                      return a0.args[0];
+                  }
+              }
               return new OperatorNode(node.op, node.fn, [a0]);
           }
+          throw new Error('never happens');
       } else if (node.op === "*") {
           if (type.isConstantNode(a0)) {
               if (a0.value === "0") {
diff --git a/test/function/algebra/simplify.test.js b/test/function/algebra/simplify.test.js
index 9e7c668bf..838e02a1a 100644
--- a/test/function/algebra/simplify.test.js
+++ b/test/function/algebra/simplify.test.js
@@ -53,6 +53,13 @@ describe('simplify', function() {
     assert.equal(fsimplified.eval()(5), 0.9933071490757153);
   });
 
+  it('should simplifyCore convert +unaryMinus to subtract', function() {
+      simplifyAndCompareEval('--2', '2');
+      var result = math.simplify('x + y + a', [math.simplify.simplifyCore], {a: -1}).toString()
+      assert.equal(result, "x + y - 1");
+  });
+
+
   it('should handle custom functions', function() {
     function doubleIt (x) { return x + x }
     var node = math.expression.node;
@@ -137,9 +144,9 @@ describe('simplify', function() {
   });
 
   it('should collect separated like factors', function() {
+    simplifyAndCompare('x*y*-x/(x^2)', '-y');
     simplifyAndCompare('x/2*x', 'x^2/2');
     simplifyAndCompare('x*2*x', '2*x^2');
-    simplifyAndCompare('x*y*-x/(x^2)', '-y');
   });
 
   it('should handle non-existing functions like a pro', function() {