Canvas polygon weird line

HTML

<canvas id="canvas" width="500" height="500"></canvas>

JavaScript

//Some basic setup ...
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
var oX = 50;
var oY = 50;
var h = 33;
var k = 50;
ctx.fillStyle = 'red';

//Draw one polygon
ctx.beginPath();
ctx.moveTo(oX,oY);
ctx.lineTo(oX=oX+k,oY=oY-h);
ctx.lineTo(oX=oX+k,oY=oY+h);
ctx.lineTo(oX=oX-k,oY=oY+h);
ctx.lineTo(oX=oX-k,oY=oY-h);
ctx.fill();
//Draw another polygon
oX = oX+k;
oY = oY+h;
ctx.beginPath();
ctx.moveTo(oX,oY);
ctx.lineTo(oX=oX+k,oY=oY-h);
ctx.lineTo(oX=oX+k,oY=oY+h);
ctx.lineTo(oX=oX-k,oY=oY+h);
ctx.lineTo(oX=oX-k,oY=oY-h);
ctx.fill();